HDU 1455 POJ 1011 Sticks 搜索

最新推荐文章于 2020-02-07 11:05:28 发布

原创最新推荐文章于 2020-02-07 11:05:28 发布 · 646 阅读

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本文探讨如何通过搜索加减枝算法解决将木棍重新组合成原始长度的问题。包括输入解析、排序、搜索策略及输出结果的实现。

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http://acm.hust.edu.cn/vjudge/problem/viewProblem.action?id=20608

**
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
这个题搜索加减枝，这个去年做过的题目，现在做起来还是手残了，敲挺久的，就在分支的计算上失误了。。。手残党。。。。不该！

#include<bits/stdc++.h>
using namespace std;
const int N = 70;
#define fi(i,n) for(int i = 0; i < n; i ++)
#define fin(i,n1,n2) for(int i = n1; i < n2; i ++)
int n, stick_sum, sum, sticks[N];
bool vis[N];
bool cmp(int a, int b) {return a > b;}

bool dfs(int cnt, int st, int len)
{
    if(cnt == n) return 1;
    int sample = -1;
    fin(i,st,n) if(!vis[i] && sticks[i] != sample)
    {
        vis[i] = 1;
        if(sticks[i] + len < stick_sum)
        {
            if(dfs(cnt + 1, i + 1, len + sticks[i])) return 1;
            else sample = sticks[i];
        }
        else if(sticks[i] + len == stick_sum)
        {
            if(dfs(cnt + 1, 0, 0)) return 1;
            else sample = sticks[i];
        }
        vis[i] = 0;
        if(!len) break;
    }
    return 0;
}

int main()
{
    while(~scanf("%d", &n), n)
    {
        sum = 0;
        memset(vis, 0, sizeof(vis));
        fi(i,n) 
        {
            scanf("%d", sticks + i);
            sum += sticks[i];
        }
        sort(sticks, sticks + n, cmp);
        for(stick_sum = sticks[0]; stick_sum <= sum; stick_sum ++)
            if(sum % stick_sum == 0 && dfs(0, 0, 0))
            {
                printf("%d\n", stick_sum);
                break;
            }
    }
    return 0;
}