poj 3253 Fence Repair(优先队列+huffman树)

     一个很长的英文背景，其他不说了，就是告诉你锯一个长度为多少的木板就要花多少的零钱，把一块足够长（不是无限长）的木板锯成n段，每段长度都告诉你了，让你求最小花费。

    明显的huffman树，优先队列是个很好的东西。

#include <stdio.h>
#include <queue>
#include <algorithm>
#include <iostream>
#include <vector>
#define ll __int64
using namespace std;

int n;
struct cmp  //优先级重载
{
    bool operator()(ll x, ll y)
    {
        return x > y;
    }
};

priority_queue<ll, vector<ll>, cmp> q;

int main()
{
    ll x;
    while (scanf("%d", &n) != EOF)
    {
        while (!q.empty()) q.pop();
        ll sum = 0;
        for (int i = 1; i <= n; i++)
        {
            cin >> x;
            sum += x;
            q.push(x);
        }
        ll ans = 0;
      //  while (!q.empty()) {printf("%d ", q.top()); q.pop();}
        while (!q.empty())
        {
            ll a = q.top();
            q.pop();
            ll b = q.top();
            q.pop();
            ans += a+b;
            x = a+b;
            if (!q.empty())
                q.push(x);
        }
        cout << ans << endl;
    }
    return 0;
}