新思路：

归并排序

代码：

# include <bits/stdc++.h>
using namespace std;
const int N = 1e5 + 10;
int a[N], b[N];
void merge(int l, int mid, int r) {
	int i = l;
	int j = mid + 1;
	int index = l;
	while (i <= mid && j <= r) {
		if (a[i] <= a[j]) {
			b[index] = a[j];
			index++;
			j++;
		} else {
			b[index] = a[i];
			index++;
			i++;
		}
	}
	while (i <= mid) {
		b[index] = a[i];
		index++;
		i++;
	}
	while (j <= r) {
		b[index] = a[j];
		index++;
		j++;
	}
	for (int i = l; i <= r; i++) {
		a[i] = b[i];
	}
}
void mergeSort(int l, int r) {
	if (l == r) {
		return;
	}
	int mid = (l + r) / 2;
	mergeSort(l, mid);
	mergeSort(mid + 1, r);
	merge(l, mid, r);
}
int main() {
	int n;
	scanf("%d", &n);
	for (int i = 1; i <= n; i++) {
		scanf("%d", &a[i]);
	}
	mergeSort(1, n);
	for (int i = n; i >= 1; i--) {
		printf("%d ", a[i]);
	}
	return 0;
}

直接sort即可

#include<bits/stdc++.h>
using namespace std;
int n;
int a[1000010];
int main(){
    cin>>n;
    for(int i=1;i<=n;i++){
        cin>>a[i];
    }
    sort(a+1,a+n+1);
    for(int i=1;i<=n;i++){
        cout<<a[i]<<" ";
    }
    return 0;
}

快排超时，归并可以用

#include<iostream>

using namespace std;

const int N=1e5+10;
int q[N],tmp[N],n;

void merge(int l,int r){
    if(l>=r) return ;
    int mid=l+r>>1;
    merge(l,mid); merge(mid+1,r);
    int k=0,i=l,j=mid+1;
    while(i<=mid&&j<=r){
        if(q[i]<=q[j]) tmp[k++]=q[i++];
        else tmp[k++]=q[j++];
    }
    while(i<=mid) tmp[k++]=q[i++];
    while(j<=r) tmp[k++]=q[j++];

    for(i=l,j=0;i<=r;i++,j++) q[i]=tmp[j];
}

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

经典板子题

#include<iostream>
#include<algorithm>
using namespace std;
int a[100005],n;
int main(){
	cin>>n;
	for(int i=0;i<=n-1;i++){
		cin>>a[i];
	}
	sort(a,a+n);
	for(int i=0;i<=n-1;i++){
		cout<<a[i]<<" ";
	}
	return 0;
}

https://www.luogu.com.cn/record/78361639

#include <iostream> #include <algorithm> using namespace std; int main() { int n; cin >>n; int a[n]; for(int i=1;i<=n;i++) { cin >>a[i]; } sort(a+1,a+1+n); for(int i=1;i<=n;i++) { cout <<a[i]<<" "; } }