uva10954Add All(貪心+優先佇列)

bigbigship發表於2014-07-22

題目連結:http://vjudge.net/contest/view.action?cid=50494#problem/D

Add All
Input:
 standard input
Output: standard output

Yup!! The problem name reflects your task; just add a set of numbers. But you may feel yourselves condescended, to write a C/C++ program just to add a set of numbers. Such a problem will simply question your erudition. So, lets add some flavor of ingenuity to it.

 

Addition operation requires cost now, and the cost is the summation of those two to be added. So, to add 1 and 10, you need a cost of 11. If you want to add 12 and 3. There are several ways

 

1 + 2 = 3, cost = 3

3 + 3 = 6, cost = 6

Total = 9

1 + 3 = 4, cost = 4

2 + 4 = 6, cost = 6

Total = 10

2 + 3 = 5, cost = 5

1 + 5 = 6, cost = 6

Total = 11

 

I hope you have understood already your mission, to add a set of integers so that the cost is minimal.

 

Input

Each test case will start with a positive number, N (2 ≤ N ≤ 5000) followed by N positive integers (all are less than 100000). Input is terminated by a case where the value of N is zero. This case should not be processed.

 

Output

For each case print the minimum total cost of addition in a single line.

 

Sample Input                           Output for Sample Input

3

1 2 3

4

1 2 3 4

0

                      

9

19


題目的意思是每次只能使兩個數相加 此次的和為這次操作的花費 最後要使所有的數加起來 求最小的花費 ,很明顯是一道貪心的題目,但是每次加法操作產生的結果也要參與進來 ,因此我們需要用到優先佇列

程式碼如下:

#include <iostream>
#include <algorithm>
#include <queue>
using namespace std;
int main()
{
    int n;
    while(cin>>n,n){
        int a;
        priority_queue<long long, vector<long long>, greater<long long> >q;//從小到大
        //過載優先順序,預設的是從大到小排列        
        for(int i=0;i<n;i++){
            cin>>a;
            q.push(a);
        }
        long long ans=0,x1,x2;
        while(!q.empty()){
           x1=q.top();
           q.pop();//注意只剩一個元素的時候
           if(q.empty())
             break;
           x2=q.top();
           q.pop();
           x1+=x2;
           ans+=x1;
           q.push(x1);
        }
        cout<<ans<<endl;
    }
    return 0;
}


相關文章