POJ 3126 Prime Path 素数筛，bfs

题目： http://poj.org/problem?id=3126

困得不行了，没想到敲完一遍直接就A了，16ms，debug环节都没进行。人品啊。

#include <stdio.h>
#include <string.h>
#include <queue>
using namespace std;

bool prime[10000];
int vis[10000];
int s, t;

void prime_init()
{
    memset(prime, 1, sizeof(prime));
    prime[1] = 0;
    for(int i = 4; i < 10000; i += 2)
        prime[i] = 0;
    for(int i = 3; i < 100; i += 2)
    {
        if(prime[i])
        {
            for(int j = i*i; j < 10000; j += i+i)
                prime[j] = 0;
        }
    }
}

queue<int>q;
void bfs()
{
    while(!q.empty())q.pop();
    memset(vis, 0, sizeof(vis));
    q.push(s);
    vis[s] = 1;
    while(!q.empty())
    {
        int u = q.front();
        q.pop();
        if(u == t)
        {
            printf("%d
", vis[u]-1);
            return;
        }
        int a = u % 10;
        int b = u % 100 - a;
        int c = u % 1000 - a - b;
        int d = u - u % 1000;
        for(int i = u-a; i <= u-a+9; i++)
        {
            if(prime[i] && !vis[i])
            {
                q.push(i);
                vis[i] = vis[u] + 1;
            }
        }
        for(int i = u-b; i <= u-b+90; i += 10)
        {
            if(prime[i] && !vis[i])
            {
                q.push(i);
                vis[i] = vis[u] + 1;
            }
        }
        for(int i = u-c; i <= u-c+900; i += 100)
        {
            if(prime[i] && !vis[i])
            {
                q.push(i);
                vis[i] = vis[u] + 1;
            }
        }
        for(int i = u-d+1000; i <= u-b+9000; i += 1000)
        {
            if(prime[i] && !vis[i])
            {
                q.push(i);
                vis[i] = vis[u] + 1;
            }
        }
    }
}

int main()
{
    prime_init();
    int n;
    scanf("%d", &n);
    while(n--)
    {
        scanf("%d %d", &s, &t);
        bfs();
    }
    return 0;
}