归并排序的实现

　　归并排序也是一种很优越的排序方式，并且时间复杂度为O(nlogn)，而且归并排序的思想很有意思很有启发，包括排序过程和时间复杂度的推导等等，具体可以google一下。下面给出二路归并的实现代码。

#include<iostream>
using namespace std;
void merge(int data[],int low,int high,int mid)
{
	int a[mid-low+1],b[high-mid];
	int i,j,k;
	for(int m = 0;m < mid-low+1;m ++)
		a[m] = data[low+m];
	for(int n = 0;n <high-mid; n ++ )
 		b[n] = data[mid+1+n];
	i = j = 0 ;
	k = low;
	while(i < mid-low+1 && j < high-mid)
		if(a[i] <= b[j])
			data[k++] = a[i++];
		else
			data[k++] = b[j++];
	while(i < mid-low+1)
		data[k++] = a[i++];
	while(j < high-mid)
		data[k++] = b[j++];
} 
void mergesort(int data[],int low,int high)
{
	int mid;
	if(low < high)
		{
			mid = int((low + high)/2);
			mergesort(data,low,mid);
			mergesort(data,mid+1,high);
			merge(data,low,high,mid);
		}
}
int main()
{
	int data[10] = {3,6,1,9,4,5,2,7,0,8};
	mergesort(data,0,9);
	for(int i = 0;i < 10;i ++)
 		cout<<data[i]<<" ";
	cout<<endl;
	return 0;
}

　　运行结果如图：