merge_sort

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

using namespace std;

const int N = 100010;
int n, a[N], tmp[N];

void merge_sort(int a[], int l, int r) {
    if (l >= r) return;
    int mid = l + r >> 1;
    merge_sort(a, l, mid), merge_sort(a, mid + 1, r);
    int i = l, j = mid + 1, k = 0;
    while (i <= mid && j <= r) {
        if (a[i] <= a[j]) tmp[k++] = a[i++];
        else tmp[k++] = a[j++];
    }
    while (i <= mid) tmp[k++] = a[i++];
    while (j <= r) tmp[k++] = a[j++];
    for (i = l, j = 0; i <= r; i++, j++) a[i] = tmp[j]; // 如果i = 0，每次归并都会打乱排好的a
}

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

    return 0;
}