排序——归并排序

1.归并思路：

2.代码实现

#include
#include

void _MergeSort(int *a,int* tmp, int left, int right)
{
	if (left >= right)
	{
		return;//递到区间只有一个元素时，即left=right时，即可返回；
	}
	int mid = (left + right) >> 1;
	_MergeSort(a, tmp, left, mid);
	_MergeSort(a, tmp, mid+1, right);
	int begin1 = left;
	int begin2 = mid + 1;
	int end1 = mid;
	int end2 = right;
	int index = left;
	while (begin1 <= end1 && begin2 <= end2)
	{
		if (a[begin1]