归并排序（从大到小）

#include<cstdio>
#include<cstdlib>
#include<iostream>
#include<algorithm>

using namespace std;

void merge(int a[], int c[], int l, int mid, int r){
	int i = l, j = mid+1, m = 1;
 	while(i <= mid && j <= r){
  		if(a[i] < a[j]) c[m++] = a[j++];
  		else c[m++] = a[i++];
    }
    while(i<=mid) c[m++] = a[i++];
	while(j<=r) c[m++] = a[j++];
	for (int k = 1; k <= r-l+1; k++)
 		a[l+k-1]=c[k];
}

void sort(int a[], int c[], int l, int r){
	if(l < r){
    	int mid=(l+r)/2;
		sort(a,c,l,mid);
		sort(a,c,mid+1,r);
		merge(a,c,l,mid,r);
	}
}

int main(){
	int n;
	scanf("%d", &n);
	int a[n+1];
	int c[n+1];
	for(int i = 0; i < n; i++)
 		scanf("%d", &a[i]);
	sort(a,c,0,n-1);

	for(int i = 0; i < n; i++)
 		printf("%d ", a[i]);
	return 0;
}