哈夫曼树 POJ 3253 Fence Repair

#include <iostream>
#include <algorithm>
#include <cstdlib>
#include <cstdio>
#include <cstring>
#include <queue>
#include <cmath>
#include <stack>
#include <map>

#pragma comment(linker, "/STACK:1024000000");
#define EPS (1e-8)
#define LL long long
#define ULL unsigned long long LL
#define _LL __LL64
#define _INF 0x3f3f3f3f
#define Mod 1000000007
#define LM(a,b) (((ULL)(a))<<(b))
#define RM(a,b) (((ULL)(a))>>(b))

using namespace std;

struct N
{
    LL ans;

    bool operator < (const N &a) const{
        return a.ans < ans;
    }
};

priority_queue<N> q;

int main()
{
    int n;

    N f,t;

    while(q.empty() == false)
        q.pop();

    while(scanf("%d",&n) != EOF)
    {
        LL sum = 0;

        while(n--)
        {
            scanf("%lld",&f.ans);
            q.push(f);
        }

        while(q.empty() == false)
        {
            f = q.top();
            q.pop();

            if(q.empty() == false)
            {
                t = q.top();
                q.pop();

                f.ans += t.ans;

                sum += f.ans;

                q.push(f);
            }
        }
        printf("%lld\n",sum);
    }
    return 0;
}