【poj3253】堆的应用

#include <iostream>
#include <stdio.h>
#include <algorithm>
#include <stdlib.h>
#define INPUT
using namespace std;
const int MAXSIZE = 50010;
bool comp1(int a,int b)
{
    return a>b;
}
int main()
{
#ifdef INPUT
    freopen("b:\\acm\\poj3253\\input.txt","r",stdin);
#endif
    long n;
    while(scanf("%d",&n) != EOF )
    {
        long v[MAXSIZE] = {0};
        unsigned long long res = 0;
      //  unsigned long long sum = 0;
        long j = 0;
        for(int i = 0 ; i < n; i++)
        {
           scanf("%ld",&v[i]);
        }
        //make_heap:[first,last),so v[n]
        make_heap(&v[0],&v[n],comp1);
        for(;n>1;n--)
        {
            //pop_heap assumes that [0..n) is already a heap
            pop_heap(&v[0],&v[n],comp1);
            //v[n-1] is now v[0],the heap is [0..n-1)
            pop_heap(&v[0],&v[n-1],comp1);
            //v[n-2] is now v[0],the heap is [0..n-2)
            v[n-2] = v[n-2] + v[n-1];
            //push_heap assumes [first,last-1) is a heap;
            //it makes [first,last) a heap(push the last - 1)
            //so,it pushes v[n-2]
            push_heap(&v[0],&v[n-1],comp1);
             res = res + v[n-2];
        }
        cout << res << endl;
        ///
    }
    return 0;
}