hdu--1455--DFS（剪枝之经典）

最新推荐文章于 2025-09-10 15:24:29 发布

转载最新推荐文章于 2025-09-10 15:24:29 发布 · 78 阅读

0 ·

CC 4.0 BY-SA版权

原文链接：http://www.cnblogs.com/haley-java/p/3244022.html

文章标签：

#数据结构与算法 #java

本文介绍了一种算法，用于解决在未知原始长度和数量的情况下，将随机切割后的木棒还原到原始状态的问题。算法通过递归搜索和回溯策略，找出最小可能的原始木棒长度。

Sticks

Time Limit: 2000/1000 MS (Java/Others) Memory Limit: 65536/32768 K (Java/Others)
Total Submission(s): 4749 Accepted Submission(s): 1313

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

#include <iostream>
#include <algorithm>
using namespace std;


int total,L;
int num,sum;
typedef struct
{
    int length;
    bool mark;
}Sticks;
Sticks sticks[70];

bool cmp(Sticks a,Sticks b)
{
    return a.length>b.length;
}
//s 已组成的木棒数目,len已经组成的长度，pos搜索的木棒的下标的位置
int dfs(int s,int len,int pos)  //(1,0,-1)
{
    if(s==total)return 1;
    for(int i=pos+1;i<num;i++)
    {        
        if(sticks[i].mark)continue;
        if(len+sticks[i].length == L)
        {
            sticks[i].mark = true;
            if(dfs(s+1,0,-1)){
            	return true;
            }
            sticks[i].mark = false;
            return false;
        }else if(sticks[i].length+len<L){
            sticks[i].mark = true;
            if(dfs(s,len+sticks[i].length,i)){
            	 return true;
            }	
            sticks[i].mark = false;           
            if(len==0)return false;         
            while(sticks[i].length==sticks[i+1].length)
				i++;
        }
    }
    return false;
}
int main()
{
    while(scanf("%d",&num)&&num!=0)
    {
        sum = 0;
        for(int i = 0; i < num; i++)
        {
        	scanf("%d",&sticks[i].length);        
            sum += sticks[i].length;
            sticks[i].mark = false;
        }       
        sort(sticks,sticks+num,cmp);       
        for(L = sticks[0].length; L <= sum; L++)
        {         
            if(sum%L!=0)continue;
            total = sum / L;
            if(dfs(1,0,-1))
            {
                printf("%d\n",L);
                break;
            }
        }
    }
    return 0;
}

 

转载于:https://www.cnblogs.com/haley-java/p/3244022.html