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;
}