poj 3253 Fence Repair 哈夫曼最优解STL解法

#include<iostream>
#include<cmath>
#include<cstdio>
#include<sstream>
#include<cstdlib>
#include<string>
#include<string.h>
#include<cstring>
#include<algorithm>
#include<vector>
#include<map>
#include<set>
#include<stack>
#include<iterator>
#include<queue>
#include<ctime>
#include<bitset>
#define eps 1e-6
#define INF 0x3f3f3f3f
#define PI acos(-1.0)
//#define ll __int64
#define ll long long
#define lson l,m,(rt<<1)
#define rson m+1,r,(rt<<1)|1
#define M 1000000007
#pragma comment(linker, "/STACK:1024000000,1024000000")
using namespace std;
int a[20005];
multiset<int> s;
multiset<int>::iterator it1;
multiset<int>::iterator it2;
int main()
{
    int n;
    while(~scanf("%d",&n))
    {
        long long ans=0;
        s.clear();
        for(int i=0;i<n;i++)
        {
            scanf("%d",&a[i]);
            s.insert(a[i]);
        }
        int tmp;
        if(n==1) {puts("0");continue;}
        while(n!=1)
        {
            it1=it2=s.begin();
            it2++;
            ans+=(*it1)+(*(it2));
            tmp=(*it1)+(*it2);
            s.erase(it1);
            s.erase(it2);
            s.insert(tmp);
            n--;
        }
        cout<<ans<<endl;
    }
    return 0;
}