归并排序板子

#include<iostream>
using namespace std;

const int N=1e5+5;

int a[N], tmp[N];
void merge_sort(int a[],int l,int r){
	if(l>=r) return; // the length of the range no more than 1, then return
	int mid=l+r>>1;
	merge_sort(a,l,mid), merge_sort(a,mid+1,r);
	int i=l, j=mid+1;
	for(int k=l;k<=r;k++)
		if(j>r || i<=mid&&a[i]<=a[j]) tmp[k]=a[i++];
		else tmp[k]=a[j++];
	for(int k=l;k<=r;k++) a[k]=tmp[k];
}

int main(){
	int n; cin>>n;
	for(int i=1;i<=n;i++) cin>>a[i];
	merge_sort(a,1,n);
	for(int i=1;i<=n;i++) cout<<a[i]<<' ';
	return 0;
}