归并排序

递归实现

#include <iostream>
#include <stdio.h>
const int maxn = 100;
int a[maxn];
void merge(int a[], int l1, int r1, int r1, int r2)
{
	int i = l1, j = l2;
	int temp[maxn], index = 0;
	while(i <= r1 && j <= r2){
		if(a[i] <= a[j])
			temp[index++] = a[i++];
		else
			temp[index++] = a[j++];
	}
	while(i <= r1)   temp[index++] = a[i++];
	while(j <= r2)   temp[index++] = a[j++];
	for(int k = 0; k < index; k++)
		a[l1 + k] = temp[k]; 
}
void mergeSort(int a[], int left, int right)
{
	if(left < right){
		int mid = (left + right) / 2;
		mergeSort(a, left, mid);
		mergeSort(a, mid + 1, right);
		merge(a, left, mid, mid + 1, right);
	}
}
int main()
{
	mergeSort(a, 0, maxn -1);
	return 0;
}