归并排序（C语言完整代码）

 归并排序是建立在归并操作上的一种有效的算法，该算法是采用分治法的一个非常典型的应用，

是一种稳定的排序算法。

将已有的子序列合并，得到完全有序的的序列；即先使每个子序列有序，再使子序列段间有序。

若将两个有序表合并成一个有序表，成为二路归并。

代码实现如下：

#include "stdio.h"
#include "malloc.h"
#include "string.h"

void PrintfArray(int* ar, int left,int right)
{
	for (int i = left; i < right; i++)
		printf("%d ", ar[i]);
}

void _MergeSort(int* ar, int left, int right,int *tmp)
{
	if (left >= right)
		return;
	int mid = (right + left) / 2;
	_MergeSort(ar, left, mid, tmp);
	_MergeSort(ar, mid + 1, right, tmp);

	int begin1 = left, end1 = mid;
	int begin2 = mid + 1, end2 = right;
	int k = left;
	while (begin1 <= end1 && begin2 <= end2)
	{
		if (ar[begin1] < ar[begin2])
			tmp[k++] = ar[begin1++];
		else
			tmp[k++] = ar[begin2++];
	}
	while (begin1 <= end1)
		tmp[k++] = ar[begin1++];
	while (begin2 <= end2)
		tmp[k++] = ar[begin2++];
	memcpy(ar + left, tmp + left, sizeof(int)*(right - left + 1));

}

void MergeSort(int* ar, int left, int right)
{
	int n = right - left;
	int* tmp = (int*)malloc(sizeof(int)*n);
	_MergeSort(ar, left, right - 1, tmp);
	free(tmp);
	tmp = NULL;

}

int main()
{
	int ar[] = {13,37,34,78,90,88,12 };
	int n = sizeof(ar) / sizeof(ar[0]);
	PrintfArray(ar, 0, n);
	MergeSort(ar,0,n);
	printf("\n");
	PrintfArray(ar, 0, n);
}