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<div id="pf1" class="pf w0 h0" data-page-no="1"><div class="pc pc1 w0 h0"><img class="bi x0 y0 w1 h1" alt="" src="https://static.pudn.com/prod/directory_preview_static/6265f1c04c65f41259206c42/bg1.jpg"><div class="c x0 y1 w2 h2"><div class="t m0 x1 h3 y2 ff1 fs0 fc0 sc0 ls0 ws0">C<span class="_ _0"> </span><span class="ff2 sc1">代码优化方案</span></div><div class="t m0 x2 h4 y3 ff2 fs1 fc0 sc0 ls0 ws0">华中科技大学计算机学院</div><div class="t m0 x3 h5 y4 ff2 fs2 fc0 sc0 ls0 ws0">姓名：<span class="ff3"> </span>王全明</div><div class="t m0 x4 h6 y5 ff3 fs3 fc0 sc0 ls0 ws0">QQ<span class="ff2">：</span> 375288012</div><div class="t m0 x3 h6 y6 ff3 fs3 fc0 sc0 ls0 ws0">Email<span class="ff2">：</span> <span class="fc1">quanming1<span class="_ _1"></span>1<span class="_ _1"></span>19@163.<span class="_ _1"></span>com</span></div></div><a class="l" rel='nofollow' onclick='return false;'><div class="d m1"></div></a></div><div class="pi" data-data='{"ctm":[1.611850,0.000000,0.000000,1.611850,0.000000,0.000000]}'></div></div>
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<div id="pf2" class="pf w0 h0" data-page-no="2"><div class="pc pc2 w0 h0"><img class="bi x0 y0 w1 h1" alt="" src="https://static.pudn.com/prod/directory_preview_static/6265f1c04c65f41259206c42/bg2.jpg"><div class="c x0 y1 w2 h2"><div class="t m0 x5 h5 y7 ff2 fs2 fc0 sc1 ls0 ws0">目录</div><div class="t m2 x6 h7 y8 ff2 fs4 fc0 sc1 ls0 ws0">目录</div><div class="t m0 x7 h8 y8 ff4 fs5 fc0 sc0 ls0 ws0">............<span class="_ _1"></span>...................<span class="_ _1"></span>...................<span class="_ _1"></span>..................<span class="_ _1"></span>...................<span class="_ _1"></span>..................<span class="_ _1"></span>...................<span class="_ _1"></span>............<span class="_ _2"></span>....<span class="_"> </span>.<span class="_ _2"></span>....<span class="_ _2"></span>....2</div><div class="t m0 x6 h8 y9 ff4 fs5 fc0 sc0 ls0 ws0">C</div><div class="t m2 x8 h7 y9 ff2 fs4 fc0 sc1 ls0 ws0">代码优化方案</div><div class="t m0 x9 h8 y9 ff4 fs5 fc0 sc0 ls0 ws0">............<span class="_ _1"></span>...................<span class="_ _1"></span>...................<span class="_ _1"></span>..................<span class="_ _1"></span>...................<span class="_ _1"></span>.......................<span class="_ _2"></span>....<span class="_ _2"></span>.....<span class="_ _2"></span>.....<span class="_ _2"></span>....<span class="_ _2"></span>.4</div><div class="t m0 xa h9 ya ff5 fs5 fc0 sc0 ls0 ws0">1<span class="ff2 sc1">、选择合适的算法和数据结构</span>..........<span class="_ _1"></span>...................<span class="_ _1"></span>..................<span class="_ _1"></span>...................<span class="_ _1"></span>..................<span class="_ _1"></span>...............4</div><div class="t m0 xa h9 yb ff5 fs5 fc0 sc0 ls0 ws0">2<span class="ff2 sc1">、使用尽量小的数据类型</span>..........<span class="_ _1"></span>...................<span class="_ _1"></span>..................<span class="_ _1"></span>...................<span class="_ _1"></span>..................<span class="_ _1"></span>.......................5</div><div class="t m0 xa h9 yc ff5 fs5 fc0 sc0 ls0 ws0">3<span class="ff2 sc1">、减少运算的强度</span>..........<span class="_ _1"></span>...................<span class="_ _1"></span>..................<span class="_ _1"></span>...................<span class="_ _1"></span>..................<span class="_ _1"></span>...................<span class="_ _1"></span>..........<span class="_ _2"></span>.....<span class="_ _2"></span>.<span class="_ _1"></span>5</div><div class="t m0 x7 h9 yd ff2 fs5 fc0 sc0 ls0 ws0">（<span class="ff3">1</span>）、查表<span class="_ _3"> </span><span class="ff3">(</span>游戏程序员必修课<span class="ff3">)........<span class="_ _1"></span>...................<span class="_ _1"></span>..................<span class="_ _1"></span>...................<span class="_ _1"></span>.....................<span class="_ _2"></span>.....5</span></div><div class="t m0 x7 h9 ye ff2 fs5 fc0 sc0 ls0 ws0">（<span class="ff3">2</span>）、求余运算<span class="_ _3"> </span><span class="ff3">........<span class="_ _1"></span>..................<span class="_ _1"></span>...................<span class="_ _1"></span>..................<span class="_ _1"></span>...................<span class="_ _1"></span>...................<span class="_ _1"></span>...........<span class="_ _2"></span>....<span class="_ _2"></span>.<span class="_ _1"></span>6</span></div><div class="t m0 x7 h9 yf ff2 fs5 fc0 sc0 ls0 ws0">（<span class="ff3">3</span>）、平方运算<span class="_ _3"> </span><span class="ff3">........<span class="_ _1"></span>..................<span class="_ _1"></span>...................<span class="_ _1"></span>..................<span class="_ _1"></span>...................<span class="_ _1"></span>...................<span class="_ _1"></span>...........<span class="_ _2"></span>....<span class="_ _2"></span>.<span class="_ _1"></span>6</span></div><div class="t m0 x7 h9 y10 ff2 fs5 fc0 sc0 ls0 ws0">（<span class="ff3">4</span>）、用移位实现乘除法运算<span class="_ _3"> </span><span class="ff3">........<span class="_ _1"></span>..................<span class="_ _1"></span>...................<span class="_ _1"></span>..................<span class="_ _1"></span>...................<span class="_ _1"></span>...........7</span></div><div class="t m0 x7 h9 y11 ff2 fs5 fc0 sc0 ls0 ws0">（<span class="ff3">5</span>）、避免不必要的整数除法<span class="_ _3"> </span><span class="ff3">........<span class="_ _1"></span>..................<span class="_ _1"></span>...................<span class="_ _1"></span>..................<span class="_ _1"></span>...................<span class="_ _1"></span>...........8</span></div><div class="t m0 x7 h9 y12 ff2 fs5 fc0 sc0 ls0 ws0">（<span class="ff3">6</span>）、使用增量和减量操作符<span class="_ _3"> </span><span class="ff3">........<span class="_ _1"></span>..................<span class="_ _1"></span>...................<span class="_ _1"></span>..................<span class="_ _1"></span>...................<span class="_ _1"></span>...........8</span></div><div class="t m0 x7 h9 y13 ff2 fs5 fc0 sc0 ls0 ws0">（<span class="ff3">7</span>）、使用复合赋值表达式<span class="_ _3"> </span><span class="ff3">........<span class="_ _1"></span>..................<span class="_ _1"></span>...................<span class="_ _1"></span>..................<span class="_ _1"></span>...................<span class="_ _1"></span>...............9</span></div><div class="t m0 x7 h9 y14 ff2 fs5 fc0 sc0 ls0 ws0">（<span class="ff3">8</span>）、提取公共的子表达式<span class="_ _3"> </span><span class="ff3">........<span class="_ _1"></span>..................<span class="_ _1"></span>...................<span class="_ _1"></span>..................<span class="_ _1"></span>...................<span class="_ _1"></span>...............9</span></div><div class="t m0 xa h9 y15 ff5 fs5 fc0 sc0 ls0 ws0">4<span class="ff2 sc1">、结构体成员的布局</span>..........<span class="_ _1"></span>...................<span class="_ _1"></span>..................<span class="_ _1"></span>...................<span class="_ _1"></span>..................<span class="_ _1"></span>...................<span class="_ _1"></span>....<span class="_ _2"></span>....<span class="_ _2"></span>..<span class="_ _1"></span>10</div><div class="t m0 x7 h9 y16 ff2 fs5 fc0 sc0 ls0 ws0">（<span class="ff3">1</span>）按数据类型的长度排序<span class="ff3">..........<span class="_ _1"></span>...................<span class="_ _1"></span>..................<span class="_ _1"></span>...................<span class="_ _1"></span>..................<span class="_ _1"></span>.............10</span></div><div class="t m0 x7 h9 y17 ff2 fs5 fc0 sc0 ls0 ws0">（<span class="ff3">2</span>）把结构体填充成最长类型长度的整倍数<span class="ff3">..........<span class="_ _1"></span>...................<span class="_ _1"></span>.......................<span class="_ _2"></span>....<span class="_ _2"></span>.....<span class="_ _2"></span>.....<span class="_ _2"></span>..10</span></div><div class="t m0 x7 h9 y18 ff2 fs5 fc0 sc0 ls0 ws0">（<span class="ff3">3</span>）按数据类型的长度排序本地变量<span class="ff3">..........<span class="_ _1"></span>...................<span class="_ _1"></span>..................<span class="_ _1"></span>...................<span class="_ _1"></span>...............1<span class="_ _1"></span>1</span></div><div class="t m0 x7 h9 y19 ff2 fs5 fc0 sc0 ls0 ws0">（<span class="ff3">4</span>）把频繁使用的指针型参数拷贝到本地变量<span class="ff3">..........<span class="_ _1"></span>...................<span class="_ _1"></span>.............<span class="_ _2"></span>.....<span class="_ _2"></span>.....<span class="_ _2"></span>....<span class="_ _2"></span>.....<span class="_ _2"></span>...<span class="_ _2"></span>1<span class="_ _1"></span>1</span></div><div class="t m0 xa h9 y1a ff5 fs5 fc0 sc0 ls0 ws0">5<span class="ff2 sc1">、循环优化</span>..........<span class="_ _1"></span>...................<span class="_ _1"></span>..................<span class="_ _1"></span>...................<span class="_ _1"></span>..................<span class="_ _1"></span>...................<span class="_ _1"></span>....................<span class="_ _2"></span>....<span class="_ _2"></span>..<span class="_ _1"></span>13</div><div class="t m0 x7 h9 y1b ff2 fs5 fc0 sc0 ls0 ws0">（<span class="ff3">1</span>）、充分分解小的循环<span class="_ _3"> </span><span class="ff3">........<span class="_ _1"></span>..................<span class="_ _1"></span>...................<span class="_ _1"></span>..................<span class="_ _1"></span>...................<span class="_ _1"></span>.................13</span></div><div class="t m0 x7 h9 y1c ff2 fs5 fc0 sc0 ls0 ws0">（<span class="ff3">2</span>）、提取公共部分<span class="_ _3"> </span><span class="ff3">........<span class="_ _1"></span>..................<span class="_ _1"></span>...................<span class="_ _1"></span>..................<span class="_ _1"></span>...................<span class="_ _1"></span>..................<span class="_ _1"></span>..<span class="_ _2"></span>.....13</span></div><div class="t m0 x7 h9 y1d ff2 fs5 fc0 sc0 ls0 ws0">（<span class="ff3">3</span>）、延时函数<span class="_ _3"> </span><span class="ff3">........<span class="_ _1"></span>..................<span class="_ _1"></span>...................<span class="_ _1"></span>..................<span class="_ _1"></span>...................<span class="_ _1"></span>...................<span class="_ _1"></span>.........<span class="_ _2"></span>.....14</span></div><div class="t m0 x7 h9 y1e ff2 fs5 fc0 sc0 ls0 ws0">（<span class="ff3">4</span>）、<span class="_ _3"> </span><span class="ff3">while<span class="_ _4"> </span></span>循环和<span class="_ _4"> </span><span class="ff3">do…while<span class="_ _4"> </span></span>循环<span class="_ _1"></span><span class="ff3">.................<span class="_ _1"></span>..................<span class="_ _1"></span>...................<span class="_ _1"></span>..........<span class="_ _2"></span>.....<span class="_ _2"></span>.....<span class="_ _2"></span>....<span class="_ _2"></span>....1<span class="_ _2"></span>4</span></div><div class="t m0 x7 h9 y1f ff2 fs5 fc0 sc0 ls0 ws0">（<span class="ff3">6</span>）、循环展开<span class="_ _3"> </span><span class="ff3">........<span class="_ _1"></span>..................<span class="_ _1"></span>...................<span class="_ _1"></span>..................<span class="_ _1"></span>...................<span class="_ _1"></span>...................<span class="_ _1"></span>.........<span class="_ _2"></span>.....15</span></div><div class="t m0 x7 h9 y20 ff2 fs5 fc0 sc0 ls0 ws0">（<span class="ff3">6</span>）、循环嵌套<span class="_ _3"> </span><span class="ff3">........<span class="_ _1"></span>..................<span class="_ _1"></span>...................<span class="_ _1"></span>..................<span class="_ _1"></span>...................<span class="_ _1"></span>...................<span class="_ _1"></span>.........<span class="_ _2"></span>.....16</span></div><div class="t m0 x7 h9 y21 ff2 fs5 fc0 sc0 ls0 ws0">（<span class="ff3">7</span>）、<span class="_ _3"> </span><span class="ff3">Switch<span class="_ _4"> </span></span>语句中根据发生频率来进行<span class="_ _4"> </span><span class="ff3">case<span class="_ _5"> </span></span>排序<span class="ff3">........<span class="_ _1"></span>..................<span class="_ _1"></span>..........................<span class="_ _2"></span>..16</span></div><div class="t m0 x7 h9 y22 ff2 fs5 fc0 sc0 ls0 ws0">（<span class="ff3">8</span>）、将大的<span class="_ _6"> </span><span class="ff3">switch<span class="_ _5"> </span></span>语句转为嵌套<span class="_ _4"> </span><span class="ff3">switch<span class="_ _4"> </span></span>语句<span class="ff3">........<span class="_ _1"></span>...................<span class="_ _1"></span>.......................<span class="_ _2"></span>....<span class="_ _2"></span>.....<span class="_ _2"></span>...<span class="_ _2"></span>17</span></div><div class="t m0 x7 h9 y23 ff2 fs5 fc0 sc0 ls0 ws0">（<span class="ff3">9</span>）、循环转置<span class="_ _3"> </span><span class="ff3">........<span class="_ _1"></span>..................<span class="_ _1"></span>...................<span class="_ _1"></span>..................<span class="_ _1"></span>...................<span class="_ _1"></span>...................<span class="_ _1"></span>.........<span class="_ _2"></span>.....19</span></div><div class="t m0 x7 h9 y24 ff2 fs5 fc0 sc0 ls0 ws0">（<span class="ff3">10</span>）、公用代码块<span class="_ _3"> </span><span class="ff3">..........<span class="_ _1"></span>...................<span class="_ _1"></span>..................<span class="_ _1"></span>...................<span class="_ _1"></span>..................<span class="_ _1"></span>.........................20</span></div><div class="t m0 x7 h9 y25 ff2 fs5 fc0 sc0 ls0 ws0">（<span class="ff3">1<span class="_ _1"></span>1<span class="ff2">）提升循环的性能</span>.......<span class="_ _1"></span>...................<span class="_ _1"></span>..................<span class="_ _1"></span>...................<span class="_ _1"></span>..................<span class="_ _1"></span>......................<span class="_ _2"></span>....20</span></div><div class="t m0 x7 h9 y26 ff2 fs5 fc0 sc0 ls0 ws0">（<span class="ff3">12</span>）、选择好的无限循环<span class="_ _3"> </span><span class="ff3">..........<span class="_ _1"></span>...................<span class="_ _1"></span>..................<span class="_ _1"></span>...................<span class="_ _1"></span>..................<span class="_ _1"></span>.............21</span></div><div class="t m0 xa h9 y27 ff5 fs5 fc0 sc0 ls0 ws0">6<span class="ff2 sc1">、提高<span class="_ _5"> </span></span>CPU<span class="_ _4"> </span><span class="ff2 sc1">的并行性</span>...............<span class="_ _1"></span>...................<span class="_ _1"></span>..................<span class="_ _1"></span>...................<span class="_ _1"></span>...................<span class="_ _1"></span>.............<span class="_ _2"></span>.....<span class="_ _2"></span>...22</div><div class="t m0 x7 h9 y28 ff2 fs5 fc0 sc0 ls0 ws0">（<span class="ff3">1</span>）使用并行代码<span class="ff3">..........<span class="_ _1"></span>...................<span class="_ _1"></span>..................<span class="_ _1"></span>...................<span class="_ _1"></span>..................<span class="_ _1"></span>...................<span class="_ _1"></span>....<span class="_ _2"></span>....<span class="_ _2"></span>..<span class="_ _1"></span>22</span></div><div class="t m0 x7 h9 y29 ff2 fs5 fc0 sc0 ls0 ws0">（<span class="ff3">2</span>）避免没有必要的读写依赖<span class="ff3">..........<span class="_ _1"></span>...................<span class="_ _1"></span>..................<span class="_ _1"></span>...................<span class="_ _1"></span>..................<span class="_ _1"></span>.........23</span></div></div><a class="l" rel='nofollow' onclick='return false;'><div class="d m1"></div></a><a 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<div id="pf3" class="pf w0 h0" data-page-no="3"><div class="pc pc3 w0 h0"><img class="bi x0 y0 w1 h1" alt="" src="https://static.pudn.com/prod/directory_preview_static/6265f1c04c65f41259206c42/bg3.jpg"><div class="c x0 y1 w2 h2"><div class="t m0 xa h9 y2a ff5 fs5 fc0 sc0 ls0 ws0">7<span class="ff2 sc1">、循环不变计算</span>..........<span class="_ _1"></span>...................<span class="_ _1"></span>..................<span class="_ _1"></span>...................<span class="_ _1"></span>..................<span class="_ _1"></span>...................<span class="_ _1"></span>............<span class="_ _2"></span>....<span class="_ _2"></span>..<span class="_ _1"></span>24</div><div class="t m0 xa h9 y2b ff5 fs5 fc0 sc0 ls0 ws0">8<span class="ff2 sc1">、函数优化</span>..........<span class="_ _1"></span>...................<span class="_ _1"></span>..................<span class="_ _1"></span>...................<span class="_ _1"></span>..................<span class="_ _1"></span>...................<span class="_ _1"></span>....................<span class="_ _2"></span>....<span class="_ _2"></span>..<span class="_ _1"></span>25</div><div class="t m0 x7 h9 y2c ff3 fs5 fc0 sc0 ls0 ws0"> <span class="ff2">（</span>1<span class="ff2">）</span>Inline<span class="_ _5"> </span><span class="ff2">函数</span>...................<span class="_ _1"></span>...................<span class="_ _1"></span>..................<span class="_ _1"></span>...................<span class="_ _1"></span>..................<span class="_ _1"></span>...................<span class="_ _1"></span>..<span class="_ _2"></span>....25</div><div class="t m0 x7 h9 y2d ff2 fs5 fc0 sc0 ls0 ws0">（<span class="ff3">2</span>）不定义不使用的返回值<span class="ff3">..........<span class="_ _1"></span>...................<span class="_ _1"></span>..................<span class="_ _1"></span>...................<span class="_ _1"></span>..................<span class="_ _1"></span>.............25</span></div><div class="t m0 x7 h9 y2e ff2 fs5 fc0 sc0 ls0 ws0">（<span class="ff3">3</span>）减少函数调用参数<span class="ff3">..........<span class="_ _1"></span>...................<span class="_ _1"></span>..................<span class="_ _1"></span>...................<span class="_ _1"></span>..................<span class="_ _1"></span>.....................25</span></div><div class="t m0 x7 h9 y2f ff2 fs5 fc0 sc0 ls0 ws0">（<span class="ff3">4</span>）所有函数都应该有原型定义<span class="ff3">..........<span class="_ _1"></span>...................<span class="_ _1"></span>..................<span class="_ _1"></span>...................<span class="_ _1"></span>..................<span class="_ _1"></span>.....26</span></div><div class="t m0 x7 h9 y30 ff2 fs5 fc0 sc0 ls0 ws0">（<span class="ff3">5</span>）尽可能使用常量<span class="ff3">(const)........<span class="_ _1"></span>...................<span class="_ _1"></span>..................<span class="_ _1"></span>...................<span class="_ _1"></span>...................<span class="_ _1"></span>...............<span class="_ _1"></span>26</span></div><div class="t m0 x7 h9 y31 ff2 fs5 fc0 sc0 ls0 ws0">（<span class="ff3">6</span>）把本地函数声明为静态的<span class="ff3">(static)..........<span class="_ _1"></span>..................<span class="_ _1"></span>...................<span class="_ _1"></span>................<span class="_ _2"></span>....<span class="_ _2"></span>.....<span class="_ _2"></span>.....<span class="_ _2"></span>....<span class="_ _2"></span>26</span></div><div class="t m0 xa h9 y32 ff5 fs5 fc0 sc0 ls0 ws0">9<span class="ff2 sc1">、采用递归</span>..........<span class="_ _1"></span>...................<span class="_ _1"></span>..................<span class="_ _1"></span>...................<span class="_ _1"></span>..................<span class="_ _1"></span>...................<span class="_ _1"></span>....................<span class="_ _2"></span>....<span class="_ _2"></span>..<span class="_ _1"></span>26</div><div class="t m0 xa h9 y33 ff5 fs5 fc0 sc0 ls0 ws0">10<span class="ff2 sc1">、变量</span>........<span class="_ _1"></span>..................<span class="_ _1"></span>...................<span class="_ _1"></span>..................<span class="_ _1"></span>...................<span class="_ _1"></span>..................<span class="_ _1"></span>...................<span class="_ _1"></span>.....<span class="_ _2"></span>.....<span class="_ _2"></span>....<span class="_ _2"></span>..27</div><div class="t m0 x7 h9 y34 ff2 fs5 fc0 sc0 ls0 ws0">（<span class="ff3">1</span>）<span class="ff3">register<span class="_ _4"> </span></span>变量<span class="ff3">........<span class="_ _1"></span>..................<span class="_ _1"></span>...................<span class="_ _1"></span>..................<span class="_ _1"></span>...................<span class="_ _1"></span>...................<span class="_ _1"></span>...<span class="_ _2"></span>....<span class="_ _2"></span>.....<span class="_ _2"></span>...27</span></div><div class="t m0 x7 h9 y35 ff2 fs5 fc0 sc0 ls0 ws0">（<span class="ff3">2</span>）、同时声明多个变量优于单独声明变量<span class="_ _3"> </span><span class="ff3">........<span class="_ _1"></span>..................<span class="_ _1"></span>.........................<span class="_ _2"></span>.....<span class="_ _2"></span>....<span class="_ _2"></span>.....<span class="_ _2"></span>.28</span></div><div class="t m0 x7 h9 y36 ff2 fs5 fc0 sc0 ls0 ws0">（<span class="ff3">3</span>）、短变量名优于长变量名，应尽量使变量名短一点<span class="_ _3"> </span><span class="ff3">........<span class="_ _1"></span>..................<span class="_ _1"></span>.....<span class="_ _2"></span>.....<span class="_ _2"></span>....<span class="_ _2"></span>.....<span class="_ _2"></span>.28</span></div><div class="t m0 x7 h9 y37 ff2 fs5 fc0 sc0 ls0 ws0">（<span class="ff3">4</span>）、在循环开始前声明变量<span class="_ _3"> </span><span class="ff3">........<span class="_ _1"></span>..................<span class="_ _1"></span>...................<span class="_ _1"></span>..................<span class="_ _1"></span>...................<span class="_ _1"></span>.........28</span></div><div class="t m0 xa h9 y38 ff5 fs5 fc0 sc0 ls0 ws0">1<span class="_ _1"></span>1<span class="ff2 sc1">、使用嵌套的<span class="_ _5"> </span></span>if<span class="_ _5"> </span><span class="ff2 sc1">结构</span>..............<span class="_ _1"></span>...................<span class="_ _1"></span>..................<span class="_ _1"></span>...................<span class="_ _1"></span>...................<span class="_ _1"></span>...............<span class="_ _2"></span>....<span class="_ _2"></span>...28</div></div><a class="l" rel='nofollow' onclick='return false;'><div class="d m1"></div></a><a class="l" rel='nofollow' onclick='return false;'><div class="d m1"></div></a><a class="l" rel='nofollow' onclick='return false;'><div class="d m1"></div></a><a class="l" rel='nofollow' onclick='return false;'><div class="d m1"></div></a><a class="l" rel='nofollow' onclick='return false;'><div class="d m1"></div></a><a class="l" rel='nofollow' onclick='return false;'><div class="d m1"></div></a><a class="l" rel='nofollow' onclick='return false;'><div class="d m1"></div></a><a class="l" rel='nofollow' onclick='return false;'><div class="d m1"></div></a><a class="l" rel='nofollow' onclick='return false;'><div class="d m1"></div></a><a class="l" rel='nofollow' onclick='return false;'><div class="d m1"></div></a><a class="l" rel='nofollow' onclick='return false;'><div class="d m1"></div></a><a class="l" rel='nofollow' onclick='return false;'><div class="d m1"></div></a><a class="l" rel='nofollow' onclick='return false;'><div class="d m1"></div></a><a class="l" rel='nofollow' onclick='return false;'><div class="d m1"></div></a><a class="l" rel='nofollow' onclick='return false;'><div class="d m1"></div></a></div><div class="pi" data-data='{"ctm":[1.611850,0.000000,0.000000,1.611850,0.000000,0.000000]}'></div></div>
<div id="pf4" class="pf w0 h0" data-page-no="4"><div class="pc pc4 w0 h0"><img class="bi x0 y0 w1 h1" alt="" src="https://static.pudn.com/prod/directory_preview_static/6265f1c04c65f41259206c42/bg4.jpg"><div class="c x0 y1 w2 h2"><div class="t m0 xb h5 y7 ff1 fs2 fc0 sc0 ls0 ws0">C<span class="_ _7"> </span><span class="ff2 sc1">代码优化方案</span></div><div class="t m0 x6 h6 y39 ff1 fs3 fc1 sc0 ls0 ws0">1<span class="ff2 sc2">、选择合适的算法和数据结构</span></div><div class="t m0 xc ha y3a ff2 fs6 fc0 sc0 ls0 ws0">选择<span class="_ _2"></span>一<span class="_ _2"></span>种合<span class="_ _2"></span>适<span class="_ _2"></span>的数<span class="_ _2"></span>据<span class="_ _2"></span>结构<span class="_ _2"></span>很重<span class="_ _2"></span>要<span class="_ _2"></span>，如<span class="_ _2"></span>果<span class="_ _2"></span>在一<span class="_ _2"></span>堆<span class="_ _2"></span>随机<span class="_ _2"></span>存<span class="_ _2"></span>放的<span class="_ _2"></span>数<span class="_ _2"></span>中使<span class="_ _2"></span>用<span class="_ _2"></span>了大<span class="_ _2"></span>量</div><div class="t m0 x6 ha y3b ff2 fs6 fc0 sc0 ls0 ws0">的插<span class="_ _2"></span>入<span class="_ _2"></span>和删<span class="_ _2"></span>除<span class="_ _2"></span>指令<span class="_ _2"></span>，<span class="_ _2"></span>那使<span class="_ _2"></span>用链<span class="_ _2"></span>表<span class="_ _2"></span>要快<span class="_ _2"></span>得<span class="_ _2"></span>多。<span class="_ _2"></span>数<span class="_ _2"></span>组与<span class="_ _2"></span>指<span class="_ _2"></span>针语<span class="_ _2"></span>句<span class="_ _2"></span>具有<span class="_ _2"></span>十<span class="_ _2"></span>分密<span class="_ _2"></span>切<span class="_ _2"></span>的关</div><div class="t m0 x6 ha y3c ff2 fs6 fc0 sc0 ls0 ws0">系，<span class="_ _2"></span>一<span class="_ _2"></span>般来<span class="_ _2"></span>说<span class="_ _2"></span>，指<span class="_ _2"></span>针<span class="_ _2"></span>比较<span class="_ _2"></span>灵活<span class="_ _2"></span>简<span class="_ _2"></span>洁，<span class="_ _2"></span>而<span class="_ _2"></span>数组<span class="_ _2"></span>则<span class="_ _2"></span>比较<span class="_ _2"></span>直<span class="_ _2"></span>观，<span class="_ _2"></span>容<span class="_ _2"></span>易理<span class="_ _2"></span>解<span class="_ _2"></span>。对<span class="_ _2"></span>于<span class="_ _2"></span>大部</div><div class="t m0 x6 ha y3d ff2 fs6 fc0 sc0 ls0 ws0">分的编译器，使用指针比使用数组生成的代码更短，执行效率更高。</div><div class="t m0 x7 ha y3e ff2 fs6 fc0 sc0 ls0 ws0">在<span class="_ _2"></span>许<span class="_ _2"></span>多<span class="_ _2"></span>种<span class="_ _2"></span>情<span class="_ _2"></span>况<span class="_ _2"></span>下<span class="_ _2"></span>，可<span class="_ _2"></span>以<span class="_ _2"></span>用<span class="_ _2"></span>指<span class="_ _2"></span>针<span class="_ _2"></span>运<span class="_ _2"></span>算<span class="_ _2"></span>代<span class="_ _2"></span>替<span class="_ _2"></span>数<span class="_ _2"></span>组<span class="_ _2"></span>索<span class="_ _2"></span>引<span class="_ _2"></span>，<span class="_ _2"></span>这<span class="_ _2"></span>样<span class="_ _2"></span>做<span class="_ _2"></span>常<span class="_ _2"></span>常<span class="_ _2"></span>能<span class="_ _2"></span>产<span class="_ _2"></span>生<span class="_ _2"></span>又<span class="_ _2"></span>快</div><div class="t m0 x6 ha y3f ff2 fs6 fc0 sc0 ls0 ws0">又短<span class="_ _2"></span>的<span class="_ _2"></span>代码<span class="_ _2"></span>。<span class="_ _2"></span>与数<span class="_ _2"></span>组<span class="_ _2"></span>索引<span class="_ _2"></span>相比<span class="_ _2"></span>，<span class="_ _2"></span>指针<span class="_ _2"></span>一<span class="_ _2"></span>般能<span class="_ _2"></span>使<span class="_ _2"></span>代码<span class="_ _2"></span>速<span class="_ _2"></span>度更<span class="_ _2"></span>快<span class="_ _2"></span>，占<span class="_ _2"></span>用<span class="_ _2"></span>空间<span class="_ _2"></span>更<span class="_ _2"></span>少。</div><div class="t m0 x6 hb y40 ff2 fs6 fc0 sc0 ls0 ws0">使用多维数组时差异更明显。下面的代码作用是相同的，<span class="ff6">但</span>是效率不一样。</div><div class="t m0 x6 ha y41 ff3 fs6 fc0 sc0 ls0 ws0"> <span class="ff2">数组索引</span> <span class="ff2">指针运算</span> </div><div class="t m0 x6 hc y42 ff3 fs6 fc0 sc0 ls0 ws0"> For(;;){ p=array </div><div class="t m0 x6 hc y43 ff3 fs6 fc0 sc0 ls0 ws0"> A=array[t++]; for(;;){ </div><div class="t m0 x6 hc y44 ff3 fs6 fc0 sc0 ls0 ws0"> a=*(p++); </div><div class="t m0 x6 ha y45 ff3 fs6 fc0 sc0 ls0 ws0"> <span class="ff2">。。。。。。。。。<span class="_ _8"> </span></span> <span class="ff2">。。。。。。<span class="_ _8"> </span></span> </div><div class="t m0 x6 hc y46 ff3 fs6 fc0 sc0 ls0 ws0"> } } </div><div class="t m0 xc hb y47 ff2 fs6 fc0 sc0 ls0 ws0">指针<span class="_ _2"></span>方法<span class="_ _2"></span>的优点<span class="_ _2"></span>是，<span class="_ _9"></span><span class="ff3">array<span class="_ _a"> </span></span>的地<span class="_ _2"></span><span class="ff6">址每<span class="_ _2"></span>次装<span class="_ _2"></span></span>入地<span class="_ _2"></span><span class="ff6">址<span class="_ _a"> </span><span class="ff3">p<span class="_"> </span></span>后</span>，在<span class="ff6">每<span class="_ _2"></span>次<span class="_ _2"></span></span>循环中<span class="_ _2"></span><span class="ff6">只需<span class="_ _2"></span></span>对</div><div class="t m0 x6 hb y48 ff3 fs6 fc0 sc0 ls0 ws0">p<span class="_ _a"> </span><span class="ff2">增量操作。在数组<span class="_ _2"></span>索引方法中，<span class="_ _2"></span><span class="ff6">每次</span>循环中都<span class="_ _2"></span>必<span class="ff6">须</span>根据<span class="_ _b"> </span></span>t<span class="_ _a"> </span><span class="ff2">值求数组下<span class="ff6">标</span>的<span class="_ _2"></span>复<span class="ff6">杂</span></span></div><div class="t m0 x6 ha y49 ff2 fs6 fc0 sc0 ls0 ws0">运算。</div></div></div><div class="pi" data-data='{"ctm":[1.611850,0.000000,0.000000,1.611850,0.000000,0.000000]}'></div></div>
<div id="pf5" class="pf w0 h0" data-page-no="5"><div class="pc pc5 w0 h0"><img class="bi x0 y0 w1 h1" alt="" src="https://static.pudn.com/prod/directory_preview_static/6265f1c04c65f41259206c42/bg5.jpg"><div class="c x0 y1 w2 h2"><div class="t m0 x6 h6 y4a ff1 fs3 fc1 sc0 ls0 ws0">2<span class="ff2 sc2">、使用尽量小的数据类型</span></div><div class="t m0 xc hb y4b ff2 fs6 fc0 sc0 ls0 ws0">能<span class="ff6">够<span class="_ _2"></span></span>使<span class="_ _2"></span>用<span class="ff6">字<span class="_ _2"></span></span>符<span class="_ _2"></span>型<span class="_ _2"></span><span class="ff3">(char)</span>定<span class="_ _2"></span>义<span class="_ _2"></span>的变<span class="_ _2"></span>量<span class="_ _2"></span>，<span class="ff6">就<span class="_ _2"></span></span>不<span class="_ _2"></span>要使<span class="_ _2"></span>用<span class="_ _2"></span>整型<span class="_ _9"></span><span class="ff3">(int)</span>变<span class="_ _2"></span>量来<span class="_ _2"></span>定<span class="_ _2"></span>义<span class="ff6">；<span class="_ _2"></span></span>能<span class="_ _2"></span><span class="ff6">够</span></div><div class="t m0 x6 hb y4c ff2 fs6 fc0 sc0 ls0 ws0">使用整<span class="_ _2"></span>型变量定<span class="_ _2"></span>义的变<span class="_ _2"></span>量<span class="ff6">就<span class="_ _2"></span></span>不要用<span class="_ _2"></span>长整型<span class="_ _c"></span><span class="ff3">(long int)<span class="_ _2"></span></span>，能不<span class="_ _2"></span>使用<span class="ff6">浮<span class="_ _2"></span></span>点型<span class="_ _9"></span><span class="ff3">(float)</span>变量</div><div class="t m0 x6 hb y4d ff6 fs6 fc0 sc0 ls0 ws0">就<span class="ff2">不<span class="_ _2"></span>要<span class="_ _2"></span>使用<span class="_ _2"></span></span>浮<span class="_ _2"></span><span class="ff2">点型<span class="_ _2"></span>变<span class="_ _2"></span>量。<span class="_ _2"></span></span>当<span class="_ _2"></span>然<span class="ff2">，<span class="_ _2"></span>在<span class="_ _2"></span>定义<span class="_ _2"></span>变<span class="_ _2"></span>量<span class="_ _2"></span></span>后<span class="ff2">不<span class="_ _2"></span>要<span class="_ _2"></span></span>超过<span class="_ _2"></span><span class="ff2">变<span class="_ _2"></span>量的<span class="_ _2"></span>作<span class="_ _2"></span>用</span>范<span class="_ _2"></span>围<span class="_ _2"></span><span class="ff2">，如<span class="_ _2"></span>果</span></div><div class="t m0 x6 hb y4e ff6 fs6 fc0 sc0 ls0 ws0">超<span class="_ _2"></span>过<span class="ff2">变<span class="_ _2"></span>量<span class="_ _2"></span>的<span class="_ _2"></span></span>范<span class="_ _2"></span>围<span class="_ _2"></span><span class="ff2">赋值<span class="_ _2"></span>，<span class="_ _9"></span><span class="ff3">C<span class="_ _a"> </span></span>编译<span class="_ _2"></span>器<span class="_ _2"></span>并<span class="_ _2"></span>不<span class="_ _2"></span></span>报<span class="_ _2"></span>错<span class="_ _2"></span><span class="ff2">，<span class="_ _2"></span></span>但<span class="ff2">程<span class="_ _2"></span>序<span class="_ _2"></span>运<span class="_ _2"></span>行<span class="_ _2"></span>结<span class="_ _2"></span>果</span>却<span class="_ _2"></span>错<span class="_ _2"></span><span class="ff2">了<span class="_ _2"></span>，<span class="_ _2"></span>而<span class="_ _2"></span></span>且<span class="_ _2"></span><span class="ff2">这<span class="_ _2"></span>样</span></div><div class="t m0 x6 hb y4f ff2 fs6 fc0 sc0 ls0 ws0">的<span class="ff6">错误</span>很<span class="ff6">难</span>发现。</div><div class="t m0 xc hb y50 ff2 fs6 fc0 sc0 ls0 ws0">在<span class="_ _a"> </span><span class="ff3">ICCA<span class="_ _d"></span>VR<span class="_ _a"> </span><span class="ff2">中，<span class="_ _2"></span>可以在<span class="_ _e"> </span></span>Options<span class="_ _a"> </span><span class="ff2">中<span class="ff6">设<span class="_ _2"></span></span>定使<span class="_ _2"></span>用<span class="_ _a"> </span></span>printf<span class="_ _a"> </span><span class="ff2">参数<span class="_ _2"></span>，尽<span class="_ _2"></span>量使<span class="_ _2"></span>用<span class="_ _2"></span><span class="ff6">基</span>本<span class="_ _2"></span>型参</span></span></div><div class="t m0 x6 hb y51 ff2 fs6 fc0 sc0 ls0 ws0">数<span class="_ _2"></span><span class="ff3">(%c<span class="_ _2"></span></span>、<span class="_ _2"></span><span class="ff3">%d<span class="_ _9"></span></span>、<span class="ff3">%x<span class="_ _9"></span></span>、<span class="ff3">%X<span class="_ _2"></span></span>、<span class="_ _9"></span><span class="ff3">%u<span class="_ _a"> </span></span>和<span class="_ _2"></span><span class="ff3">%s<span class="_"> </span><span class="ff6">格</span></span>式<span class="_ _9"></span>说明<span class="_ _2"></span>符<span class="_ _9"></span><span class="ff3">)<span class="_ _2"></span></span>，<span class="_ _2"></span>少<span class="_ _2"></span>用<span class="_ _2"></span>长<span class="_ _2"></span>整<span class="_ _9"></span>型参<span class="_ _9"></span>数<span class="_ _9"></span><span class="ff3">(%ld</span>、<span class="_ _2"></span><span class="ff3">%lu<span class="_ _9"></span></span>、</div><div class="t m0 x6 hb y52 ff3 fs6 fc0 sc0 ls0 ws0">%lx<span class="_ _a"> </span><span class="ff2">和<span class="_ _2"></span></span>%lX<span class="_ _a"> </span><span class="ff6">格<span class="ff2">式<span class="_ _2"></span>说<span class="_ _2"></span>明符<span class="_ _2"></span></span></span>)<span class="_ _2"></span><span class="ff2">，<span class="_ _2"></span><span class="ff6">至</span>于<span class="_ _2"></span><span class="ff6">浮<span class="_ _2"></span></span>点型<span class="_ _2"></span>的<span class="_ _2"></span>参数<span class="_ _2"></span></span>(%f)<span class="_ _2"></span><span class="ff2">则尽<span class="_ _2"></span>量<span class="_ _2"></span>不要<span class="_ _2"></span>使<span class="_ _2"></span>用，<span class="_ _2"></span><span class="ff6">其<span class="_ _2"></span>它<span class="_ _a"> </span></span></span>C<span class="_"> </span><span class="ff2">编译</span></div><div class="t m0 x6 hb y53 ff2 fs6 fc0 sc0 ls0 ws0">器<span class="ff6">也</span>一样。<span class="_ _2"></span>在<span class="ff6">其它条件</span>不<span class="_ _2"></span>变的情况下，使用<span class="_ _c"></span><span class="ff3">%f<span class="_ _4"> </span></span>参<span class="_ _2"></span>数，<span class="ff6">会</span>使生成<span class="_ _2"></span>的代码的数量增</div><div class="t m0 x6 hb y54 ff6 fs6 fc0 sc0 ls0 ws0">加<span class="ff2">很多，执行速度</span>降低<span class="ff2">。</span></div><div class="t m0 x6 h6 y55 ff1 fs3 fc1 sc0 ls0 ws0">3<span class="ff2 sc2">、减少运算的强度</span></div><div class="t m0 x6 hd y56 ff2 fs7 fc2 sc3 ls0 ws0">（<span class="ff1 sc0">1</span>）、查表<span class="_ _f"> </span><span class="ff1 sc0">(</span>游戏程序员必修课<span class="ff1 sc0">)</span></div><div class="t m0 xc hb y57 ff2 fs6 fc0 sc0 ls0 ws0">一个<span class="_ _2"></span><span class="ff6">聪<span class="_ _2"></span></span>明的<span class="_ _2"></span>游<span class="_ _2"></span>戏大<span class="_ _2"></span><span class="ff6">虾<span class="_ _2"></span></span>，<span class="ff6">基<span class="_ _2"></span></span>本<span class="_ _2"></span><span class="ff6">上</span>不<span class="_ _2"></span><span class="ff6">会<span class="_ _2"></span></span>在<span class="_ _2"></span><span class="ff6">自己<span class="_ _2"></span></span>的<span class="_ _2"></span><span class="ff6">主</span>循<span class="_ _2"></span>环<span class="_ _2"></span><span class="ff6">里搞<span class="_ _2"></span>什<span class="_ _2"></span>么</span>运<span class="_ _2"></span>算<span class="_ _2"></span><span class="ff6">工</span>作<span class="_ _2"></span>，<span class="_ _2"></span><span class="ff6">绝</span></div><div class="t m0 x6 hb y58 ff2 fs6 fc0 sc0 ls0 ws0">对是<span class="ff6">先</span>计算好了，<span class="ff6">再</span>到循环<span class="ff6">里</span>查表。<span class="ff6">看</span>下面的<span class="ff6">例</span>子：</div><div class="t m0 x6 hb y59 ff6 fs6 fc0 sc0 ls0 ws0">旧<span class="ff2">代码：</span></div><div class="t m0 x6 hc y5a ff3 fs6 fc0 sc0 ls0 ws0"> long factorial(int i)</div><div class="t m0 x6 hc y5b ff3 fs6 fc0 sc0 ls0 ws0"> {</div><div class="t m0 x6 hc y5c ff3 fs6 fc0 sc0 ls0 ws0"> if (i == 0)</div><div class="t m0 x6 hc y5d ff3 fs6 fc0 sc0 ls0 ws0"> return 1;</div><div class="t m0 x6 hc y5e ff3 fs6 fc0 sc0 ls0 ws0"> else</div><div class="t m0 x6 hc y5f ff3 fs6 fc0 sc0 ls0 ws0"> return i * factorial(i - 1);</div><div class="t m0 x6 hc y60 ff3 fs6 fc0 sc0 ls0 ws0"> }</div><div class="t m0 x6 hb y61 ff6 fs6 fc0 sc0 ls0 ws0">新<span class="ff2">代码：</span></div><div class="t m0 x6 hc y62 ff3 fs6 fc0 sc0 ls0 ws0"> static long factorial_table[] =</div><div class="t m0 x6 ha y63 ff3 fs6 fc0 sc0 ls0 ws0"> {1<span class="ff2">，</span> 1<span class="ff2">，</span> 2<span class="ff2">，</span> 6<span class="ff2">，</span> 24<span class="ff2">，</span> 120<span class="ff2">，</span> 720 /* etc */ };</div><div class="t m0 x6 hc y64 ff3 fs6 fc0 sc0 ls0 ws0"> long factorial(int i)</div><div class="t m0 x6 hc y65 ff3 fs6 fc0 sc0 ls0 ws0"> {</div><div class="t m0 x6 hc y66 ff3 fs6 fc0 sc0 ls0 ws0"> return factorial_table[i];</div></div></div><div class="pi" data-data='{"ctm":[1.611850,0.000000,0.000000,1.611850,0.000000,0.000000]}'></div></div>
