JOJ1534: Sticks（麻烦的剪枝）

最新推荐文章于 2017-03-18 14:15:28 发布

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本文介绍了一道算法题目，旨在寻找被随机切割后的棍子的最短原始长度。输入包括切割后的棍子部分数量及各部分长度，输出则是计算得出的最小可能原始长度。文章提供了完整的C++代码实现，采用深度优先搜索策略解决问题。

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;
}