JOJ1534: Sticks（麻烦的剪枝）

 

Status	In/Out	TIME Limit	MEMORY Limit	Submit Times	Solved Users	JUDGE TYPE
	stdin/stdout	3s	8192K	942	143	Standard

George took sticks of the same length and cut them randomly until all parts became at most 50 units long. Now he wants to return sticks to the original state, but he forgot how many sticks he had originally and how long they were originally. Please help him and design a program which computes the smallest possible original length of those sticks. All lengths expressed in units are integers greater than zero.

Input

The input file contains blocks of 2 lines. The first line contains the number of sticks parts after cutting. The second line contains the lengths of those parts separated by the space. The last line of the file contains zero.

Output

The output file contains the smallest possible length of original sticks, one per line.

Sample Input

 

9
5 2 1 5 2 1 5 2 1
4
1 2 3 4
0

Sample Output

 

6
5

 

 

This problem is used for contest: 119  150 

 

#include<stdio.h>
#include<algorithm>
using namespace std;
bool visit[100],flag;
int a[100],n,sum,beg;
bool cmp(int a,int b)
{
 return a>b;
}
void dfs(int depth,int sheng)
{
 if(depth==n&&sheng==0)
 {
  flag=true;
  return;
 }
 if(flag) return;
 if(sheng==0) sheng=beg;
 for(int i=0;i<n&&!flag;i++)
 if(!visit[i]&&a[i]<=sheng)
 {
  visit[i]=true;
  dfs(depth+1,sheng-a[i]);
  visit[i]=false;
  if(sheng==beg||a[i]==sheng||flag) break;//这个剪枝让我很无语
 }
}
int main()
{
 //freopen("in.txt","r",stdin);
 //freopen("out.txt","w",stdout);
 int i;
 while((scanf("%d",&n),n)!=0)
 {
  sum=0;
  flag=false;
  for(i=0;i<n;i++)  
  {
   scanf("%d",&a[i]);
   visit[i]=false;
   sum+=a[i];
  }
        sort(a,a+n,cmp);
  beg=a[0]-1;
  while(beg<=sum)
  {
   beg++;
   if(sum%beg!=0) continue;
   dfs(0,beg);
   if(flag)
   {
    printf("%d/n",beg);
    break;
   }
  }  
 }
 return 0;
}