POJ3253(贪心)

1.要考虑到规模为20，000 累加起来肯定会超的，要用long long
2. 思想就是先从正着推，一定是先切掉最长的那块，这样之后都不会受影响;再反着来想，就是先合并最小的

//#define LOCAL

#include <cstdio>
#include <cstring>
#include <algorithm>
#include <queue>
#define N 20000

using namespace std;

int main(void){
#ifdef LOCAL
    freopen("data.in", "r", stdin);
#endif
    int n;
    long long temp;
    priority_queue<long long, vector<long long >, greater<long long> > q;

    scanf("%d", &n);
    for(int i = 0; i < n; i++){
        scanf("%lld", &temp);
        q.push(temp);
    }

    if(q.size() == 1)
        printf("%lld\n", q.top());
    else{
        long long ans = 0;
        while(q.size() > 1){
            int x = q.top();
            q.pop();
            int y = q.top();
            q.pop();

            //printf("x:%d y:%d\n", x, y);

            int xy = x + y;
            ans += xy;
            q.push(xy);
        }

        printf("%lld\n", ans);
    }

    return 0;
}