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  • 小木棍

    这是一道很好的剪枝题目

    #include<cstdio>
    #include<iostream>
    #include<cstring>
    #include<algorithm>
    using namespace std;
    int n,x,t,maxx,len,cnt,sum;
    bool v[105];
    int a[105];
    inline bool dfs(int stick,int cab,int last){
        if(stick>cnt)return true;//全部拼好了返回true
        if(cab==len)return dfs(stick+1,0,1);//这一根拼好了就拼下一根
        int fail=0;
        for(int i=last;i<=n;i++){
            if(!v[i]&&cab+a[i]<=len&&fail!=a[i]){//如果没用过而且不超过原有长度并且不存在等效冗余
                v[i]=1;//打上标记以防再次用到
                if(dfs(stick,cab+a[i],i+1))return true;//能拼好就return true
                fail=a[i];
                v[i]=0;
                if(cab==0||cab+a[i]==len)return false;//如果一开始就拼不了不管到哪里也还是拼不了,如果拼完了还是不行,小碎块也拼不起来
            }
        }
        return false;//所有都尝试过,返回错误
    }
    int main(){
        while(scanf("%d",&n)&&n){
         maxx=sum=0;
         for(int i=1;i<=n;i++){
             scanf("%d",&a[i]);
            maxx=max(a[i],maxx);
            sum+=a[i];
         }    
         sort(a+1,a+n+1);reverse(a+1,a+n+1);
         for(len=maxx;len<=sum;len++){//从最长的木棍开始
            if(sum%len)continue;
            cnt=sum/len;
            memset(v,0,sizeof(v));记得清零
            if(dfs(1,0,1)){printf("%d
    ",len);break;}//找到了就退出
         }
        }
        return 0;
    }
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  • 原文地址:https://www.cnblogs.com/coder-cjh/p/11483599.html
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