改进的基于c++的归并排序算法。排序算法大体可分为两种： 　　　　一种是比较排序，时间复杂度O(nlogn) ~ O(n^2)，主要有：冒泡排序，选择排序，插入排序，归并排序，堆排序，快速排序等。 　　　　另一种是非比较排序，时间复杂度可以达到O(n)，主要有：计数排序，基数排序，桶排序等。(Improved c ++ based merge sort algorithm. There are two kinds of sorting algorithms: one is sorting, the time complexity is O (nlogn) ~ O (n ^ 2), and there are three types: sorting by bubble, sorting by sorting, sorting by sorting, sorting by heap, sorting by heap Sort and so on. The other is non-comparison, the time complexity can reach O (n), there are: count sort, base sort, bucket sort and so on.)