不要相信下面的代码！ 这才是正确的：

#include <iostream>
#include <algorithm>
using namespace std;
int n, a[1005];
int main() {
    freopen("gravity.in", "r", stdin);
    freopen("gravity.out", "w", stdout);
    cin >> n;
    for (int i = 0; i < n; i++)
        cin >> a[i];
    sort(a, a + n);
    for (int i = 0; i < n; i++)
        cout << a[i] << ' ';
    return 0;
}
作者修改了一小部分

#include <iostream>
#include <algorithm>
using namespace std;
int n, a[1005];
int main() {
    freopen("gravity.in", "r", stdin);
    freopen("gravity.out", "w", stdout);
    cin >> n;
    for (int i = 0; i < n; i++)
        cin >> a[i];
    sort(a, a + n);
    for (int i = 0; i < n; i++)
        cout << a[i] << ' ';
    return 0;
}