说明：  刚才传错了……这个才是采用蒙特卡罗法计算pi的近似值的源程序。方法是随机产生二维0~1之间的均匀分布数据点，计算落在单位圆内的点与总点数之比就是pi的近似值
(Chuan just wrong ... ... this is the Monte Carlo method to calculate pi approximation of the source. Is randomly generated from 0 to 1 between two-dimensional uniformly distributed data points, the calculation falls within the unit circle with the ratio of the total points is the approximation of pi)