NC16663 合并果子

贪心思想，每次都选最轻的两堆
采用优先队列实现。

#include <iostream>
using namespace std;
int n;
const int maxn = 10010;
int arr[maxn];
int total = 0;
void push(int x) {
    total++;
    arr[total] = x;
    int j = total;
    int i = j / 2;
    while (i > 0 && arr[j] < arr[i]) {
        swap(arr[i], arr[j]);
        j = i;
        i = j / 2;
    }
}

int top() {
    return arr[1];
}
void pop() {
    arr[1] = arr[total];
    total--;
    int i = 1;
    int j = i * 2;
    if (j + 1 <= total && arr[j + 1] < arr[j])j = j + 1;
    while (j <=total&&arr[j]<arr[i]) {
        swap(arr[i], arr[j]);
        i = j;
        j = i * 2;
        if (j + 1 <= total && arr[j + 1] < arr[j])j = j + 1;
    }
}
int main()
{
    cin >> n;
    for (int i = 1; i <= n; i++) {
        int x;
        cin >> x;
        push(x);
    }
    int ans = 0;
    for (int i = 1; i < n; i++) {
        int x = top();
        pop();
        int y = top();
        pop();
        ans += x + y;
        push(x + y);
    }
    cout << ans;

}