参考答案：

#include<iostream>

using namespace std;

const int N = 200010;
int 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 k = 0; int i = l, j = mid + 1;

    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 (int i = l, j = 0; i <= r; ++i, ++j) a[i] = tmp[j];
}
int main()
{
    int n;
    cin >> n;

    for (int i = 0; i < n; ++i) scanf("%d", &a[i]);

    merge_sort(a, 0, n - 1);

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

    return 0;
}