HDU 1016 Prime Ring Problem 搜索题

#include<stdio.h>
#include<string.h>
#include <iostream>
using namespace std;
int N;
int prime[12]={2,3,5,7,11,13,17,19,23,29,31,37};
int ring[25];
int visited[25];
int search(int low ,int high,int x)
{
    if(low>high)return 0;
    int mid=(low+high)>>1;
    if(x==prime[mid])return mid;
    else if(x>prime[mid])
    {
        return search(mid+1,high,x);
    }
    return search(low,mid-1,x);
}
void DFS(int index,int primNum)
{
    int i;
    if(primNum==N&&search(1,11,index+1))
    {
        for( i=1;i<N;i++)
        {
            printf("%d ",ring[i]);
        }
        printf("%d\n",ring[N]);
        return ;
    }
    for(i=1;i<=N;i++)
    {
        if(!visited[i]&&((index&1)!=(i&1))&& search(1,11,index+i))
        {
            visited[i]=1;
            ring[primNum+1]=i;
            DFS(i,primNum+1);
            visited[i]=0;
            ring[primNum+1]=0;
        }
    }

}
int main()
{
    int cases=0;
    while(scanf("%d",&N)!=EOF)
    {
        cases++;
        memset(ring,0,sizeof(ring));
        memset(visited,0,sizeof(visited));
        printf("Case %d:\n",cases);
        visited[1]=1;
        ring[1]=1;
        DFS(1,1);
        printf("\n");
    }
    return 0;
}