中文说明：该代码包含了nsgaII算法的crowding-distance的代码，可以把它和传统GA算法代码镶嵌使用，用于求解多目标规划问题，可以显著提高GA算法在求解多目标问题时的速率
English Description：
The code contains the code of crowding distance of nsgaii algorithm. It can be embedded with the code of traditional GA algorithm to solve multi-objective programming problems, which can significantly improve the speed of GA algorithm in solving multi-objective problems