说明：  K近邻分类器，用于模式识别等领域，该程序短小精悍，适合与ANN和SVM进行比较研究，本人多篇论文用到，效果较好。
(K-nearest neighbor classifier is often used in pattern recognition and other fields. It is suitful for a comparative study with ANN and SVM. I have published some papers used the code. The effect is good.)