poj 3126 Prime Path 簡單bfs

注意千位的時候要從1開始

#include <algorithm>
#include <iostream>
#include <stdio.h>
#include <queue>
#include <string.h>
#include <math.h>
using namespace std;
struct node
{
    int x;
    int step;
};
int book[10000];
int n, m;
bool judge(int x)
{
//    for(int i = 2;i <= sqrt(x);i++){
//        if(x%i==0)
//            return false;
//    }
//    return true;
    int i;
    if(x==1||x==0||x==2)
        return 0;
    else
    {
            for(i=2;i<=sqrt(x);i++)
       {
              if(x%i==0)
              return 0;
       }
       return 1;

    }
}
int BFS()
{
    node a,  ans;
    queue<node>Q;
    ans.x = n;
    ans.step = 0;
    Q.push(ans);
    book[n] = 1;
    int x, i;
    while(!Q.empty()){
        a = Q.front();
        Q.pop();
        if(a.x == m){
            return a.step;
        }
        for(i = 0;i < 10;i++){//個位
            x = a.x/10*10+i;
            if(judge(x)&&!book[x]){
                ans.step = a.step+1;
                ans.x = x;
                book[x] = 1;
                Q.push(ans);
            }
        }
        for(i = 0;i < 10;i++){//十位
            x = a.x/100*100+i*10+a.x%10;
            if(judge(x)&&!book[x]){
                ans.step = a.step+1;
                ans.x = x;
                book[x] = 1;
                Q.push(ans);
            }
        }
        for(i = 0;i < 10;i++){//百位
            x = a.x/1000*1000+i*100+a.x%100;
            if(judge(x)&&!book[x]){
                ans.step = a.step+1;
                ans.x = x;
                book[x] = 1;
                Q.push(ans);
            }
        }
        for(i = 1;i < 10;i++){//千位
            x = i*1000+a.x%1000;
            if(judge(x)&&!book[x]){
                ans.step = a.step+1;
                ans.x = x;
                book[x] = 1;
                Q.push(ans);
            }
        }
    }
    return -1;
}
int main()
{
    int t;
    scanf("%d", &t);
    while(t--){
        memset(book,0,sizeof(book));
        scanf("%d %d", &n, &m);
        int ans = BFS();
        if(ans==-1){
            printf("Impossible\n");
        }else {
            printf("%d\n", ans);
        }
    }

    return 0;
}