归并排序

归并排序：利用"归并"技术来进行排序。归并是指将若干个已排序的子文件合并成一个有序的文件。可以用于外排序。

# include <stdio.h>
void merge_sort(int a[],int b[],int low,int high);
void merge(int a[],int b[],int low,int mid,int high);
int main(void)
{
	int a[]={4165,46,41,984,531,6,4653,6,46,4,64,63};
	int b[100];		//辅助数组 
	merge_sort(a,b,0,sizeof(a)/sizeof(a[0])-1); 
	for (int i=0;i<sizeof(a)/sizeof(a[0]);++i)
	printf ("%d ",a[i]);
	
	return 0;
}

void merge_sort(int a[],int b[],int low,int high)
{
	if (low >= high)
	return;
	int mid = (low+high)/2;			
	merge_sort(a,b,low,mid);		//分治法 
	merge_sort(a,b,mid+1,high);		////分治法 
	merge(a,b,low,mid,high);
}

void merge(int a[],int b[],int low,int mid,int high)
{
	int i,j,k;
	for (i=low;i<=high;++i)
	b[i] = a[i];
	i = low;
	j = mid+1;
	k = low;
	while(i <= mid && j <= high)		//将b中的数据排序后存入a中 
	{
		if (b[i] <= b[j])
		a[k++] = b[i++];
		else
		a[k++] = b[j++];
	}
	while(i<=mid)		//将b中i~mid中的剩余元素存入a中 
	a[k++] = b[i++];
	while(j<=high)		//将b中mid~high中的剩余元素存入a中 
	a[k++] = b[j++];
}