堆排序

输入一个长度为 n 的整数数列，从小到大输出前 m 小的数。

#include <iostream>
using namespace std;
const int N = 1e5 + 10;
int n, m, len;
int h[N];

void down (int u) {
    int t = u;
    int l = u * 2, r = u * 2 + 1;
    if (l <= len && h[l] <= h[t]) t = l;
    if (r <= len && h[r] <= h[t]) t = r;
    if (t != u) {
        swap (h[t], h[u]);
        down (t);
    }
}

int main() {
    cin >> n >> m;
    len = n;
    for (int i = 1; i <= n; i++) cin >> h[i];
    
    for (int i = n / 2; i; i--) down (i);
    
    while (m--) {
        cout << h[1] << " ";
        h[1] = h[len--];
        down (1);
    }
    return 0;
}