Fence Repair POJ - 3253 (욕심!! 하프만 최소 두 갈래 나무)

 Fence Repair

 
POJ - 3253 
Farmer John wants to repair a small length of the fence around the pasture. He measures the fence and finds that he needs N (1 ≤ N ≤ 20,000) planks of wood, each having some integer length Li (1 ≤ Li ≤ 50,000) units. He then purchases a single long board just long enough to saw into the N planks (i.e., whose length is the sum of the lengths Li). FJ is ignoring the "kerf", the extra length lost to sawdust when a sawcut is made; you should ignore it, too.
FJ sadly realizes that he doesn't own a saw with which to cut the wood, so he mosies over to Farmer Don's Farm with this long board and politely asks if he may borrow a saw.
Farmer Don, a closet capitalist, doesn't lend FJ a saw but instead offers to charge Farmer John for each of the N-1 cuts in the plank. The charge to cut a piece of wood is exactly equal to its length. Cutting a plank of length 21 costs 21 cents.
Farmer Don then lets Farmer John decide the order and locations to cut the plank. Help Farmer John determine the minimum amount of money he can spend to create the Nplanks. FJ knows that he can cut the board in various different orders which will result in different charges since the resulting intermediate planks are of different lengths.
Input
Line 1: One integer 
N, the number of planks 
Lines 2.. 
N+1: Each line contains a single integer describing the length of a needed plank
Output
Line 1: One integer: the minimum amount of money he must spend to make 
N-1 cuts
Sample Input

3
8
5
8

Sample Output

34

Hint
He wants to cut a board of length 21 into pieces of lengths 8, 5, and 8. 
The original board measures 8+5+8=21. The first cut will cost 21, and should be used to cut the board into pieces measuring 13 and 8. The second cut will cost 13, and should be used to cut the 13 into 8 and 5. This would cost 21+13=34. If the 21 was cut into 16 and 5 instead, the second cut would cost 16 for a total of 37 (which is more than 34).
제목: 한 번 찍을 때마다 한 번 베기 전의 길이를 더해서 가장 작은 것이 얼마인지 물어본다.
사고방식: 이것은 가장 작은 두 갈래 나무 문제입니다. HuffmanTree 사상은:
(1) 입력한 모든 원소를 순서대로 정렬한 다음에 가장 작은 두 원소를 선택하여 그들의 값과 값을 총 비용으로 누적시킨다
(2) 이 두 개의 최소 원소를 대열에서 내보내고 그들의 값을 대열에 넣고 모든 원소를 다시 배열하며 중복(1), 대열의 원소 개수<=1까지 누적된 비용은 최소 비용이다
AC 코드:

#include
#include
#include
#include
#include
#define maxn 50010
using namespace std;

int a[maxn];
int main()
{
	long long sum;
	int n,i,j,t;
	scanf("%d",&n);
	sum=0;
	for(i=1;i<=n;++i){
		scanf("%d",&a[i]);
	}
	sort(a+1,a+n+1);
	for(i=1;i<=n-1;++i){	// ，  
		t=a[i]+a[i+1];
		sum+=t;
		for(j=i+2;j<=n;++j){
			if(t>a[j]){
				a[j-1]=a[j];
				if(j==n){
					a[n]=t;
					break;
				}
			}
			else{
				a[j-1]=t;
				break;
			}
		}
	}
	printf("%lld
",sum);	
	return 0;
}