HDU 1016 Prime Ring Problem

转载请注明出处：http://blog.csdn.net/a1dark

分析：直接DFS暴力搜索就行了、由于运行时间比较小就没去剪枝了、简单题不懂看代码

 

#include<stdio.h>

#include<string.h>

int map[25];

int vis[25];

int n,flag,cas;

int judge(int x){

    if(x%2==0)return 0;

    for(int i=2;i<=x/2;i++){

        if(x%i==0)

            return 0;

    }

    return 1;

}

void dfs(int cur){

    vis[1]=1;

    if(cur>n&&judge(map[n]+1)){

        if(flag==0){

            printf("Case %d:\n",cas);cas++;

            flag++;

        }

        for(int i=1;i<n;i++)

            printf("%d ",map[i]);

        printf("%d\n",map[n]);

    }

    else{

        for(int i=2;i<=n;i++){

            map[cur]=i;

            if(!vis[i]&&judge(map[cur]+map[cur-1])){

                vis[i]=1;

                dfs(cur+1);

                vis[i]=0;

            }

        }

    }

}

int main(){

    cas=1;

    while(scanf("%d",&n)!=EOF){

        if(n==1){

            printf("Case %d:\n",cas);cas++;

            printf("1\n");continue;

        }

        flag=0;

        memset(vis,0,sizeof(vis));

        memset(map,0,sizeof(map));

        map[1]=1;

        dfs(2);

        printf("\n");

    }

    return 0;

}