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:
",cas);cas++;
            flag++;
        }
        for(int i=1;i<n;i++)
            printf("%d ",map[i]);
        printf("%d
",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:
",cas);cas++;
            printf("1
");continue;
        }
        flag=0;
        memset(vis,0,sizeof(vis));
        memset(map,0,sizeof(map));
        map[1]=1;
        dfs(2);
        printf("
");
    }
    return 0;
}