暴搜+回溯 —— Sticks

Sticks

Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 65536/32768 K (Java/Others)
Total Submission(s): 8682    Accepted Submission(s): 2561

Problem Description

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 contains blocks of 2 lines. The first line contains the number of sticks parts after cutting, there are at most 64 sticks. 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
  
  

题意：将n个数分成m堆，每一堆的和都相等为H，求H最小为多少。
题中有一些数字：
50：指剪后每一段绳子长度最大为50
64：指剪后绳子数量最大为64
还有注意，有可能有绳子根本就没有减

剪枝：

（1）剩余长度和当前长度相等时，停止搜索

（2）剩余长度等于绳子总长度，当前长度不符合，则停止搜索

（3）当前长度不符合条件，则相同的长度不再进行搜索

#include<stdio.h>
#include<iostream>
#include<string.h>
#include<algorithm>
using namespace std;
int flag,n,maxn;
int used[100],a[100];
int cmp(int x,int y){
    return x>y;
}
void dfs(int ans,int num_k,int dd)
{
    if(flag==1) return ;
    if(num_k==n){
        flag=1;
        return ;
    }
    if(ans==0 && num_k<n)   dfs(maxn,num_k,0);
    
    for(int i=dd;i<n;i++){
        if(!flag && !used[i] && a[i]<=ans){
            used[i]=1;
            dfs(ans-a[i],num_k+1,dd);
            used[i]=0;
            if(ans==a[i])return ;
            if(ans==maxn)   return ;
            while(a[i]==a[i+1]) ++i ;
        }
    }
}
int main()
{
    while(~scanf("%d",&n)){
        if(n==0)    break;
        int sum=0;
        for(int i=0;i<n;i++){
            scanf("%d",&a[i]);
            sum+=a[i];
        }
        sort(a,a+n,cmp);
        maxn=a[0];
        flag=0;
        while(!flag){
            while(sum%maxn!=0)
                ++maxn;
            memset(used,0,sizeof(used));
            dfs(maxn,0,0);
            if(flag)    break;
            ++maxn;
        }
        printf("%d\n",maxn);
    }
    return 0;
}