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：