POJ3126——BFS——Prime Path

/************************************************
* Author        :Powatr
* Created Time  :2015-8-9 16:09:31
* File Name     :F.cpp
************************************************/

#include <cstdio>
#include <algorithm>
#include <iostream>
#include <sstream>
#include <cstring>
#include <cmath>
#include <string>
#include <vector>
#include <queue>
#include <deque>
#include <stack>
#include <list>
#include <map>
#include <set>
#include <bitset>
#include <cstdlib>
#include <ctime>
using namespace std;

#define lson l, mid, rt << 1
#define rson mid + 1, r, rt << 1 | 1
typedef long long ll;
const int MAXN = 1e5 + 10;
const int INF = 0x3f3f3f3f;
const int MOD = 1e9 + 7;
int a[5], b[5];
int vis[110150];
queue<pair<int, int> > q;
int prim[21015];
void inti()
{
for(int i = 1000; i < 10000; i++){
for(int j = 2; j <i/2; j++){
if(i%j == 0)  {prim[i] = 1;break;}
}
}

}
int main(){
int T;
int n, m;
memset(prim, 0, sizeof(prim));
scanf("%d", &T);
inti();
while(T--){
memset(vis, 0, sizeof(vis));
scanf("%d%d", &n, &m);
a[1] = n/1000, a[2] = n%1000/100, a[3] = n%100/10, a[4] = n%10;
while(!q.empty()) q.pop();
q.push(make_pair(n, 0));
while(!q.empty()){
int x = q.front().first, y = q.front().second;
q.pop();
if(vis[x]) continue;
vis[x] = 1;
// printf("%d\n", x);
a[1] = x/1000, a[2] = x%1000/100, a[3] = x%100/10, a[4] = x%10;
if(x == m){
printf("%d\n", y);
break;
}
for(int i = 1; i <= 9; i++){
int k = i*1000 + a[2]*100 + a[3]*10 + a[4];
if(!prim[k])
q.push(make_pair(k,y+1));
}
for(int i = 0; i <= 9; i++){
int k = a[1]*1000 + i*100 + a[3]*10 + a[4];
if(!prim[k])
q.push(make_pair(k, y+1));
}
for(int i = 0 ; i <= 9; i++){
int k = a[1]*1000 + a[2]*100 + i*10 + a[4];
if(!prim[k])
q.push(make_pair(k,y+1));
}
for(int i = 0; i <= 9; i++){
int k = a[1]*1000 + a[2]*100 + a[3]*10 + i;
if(!prim[k])
q.push(make_pair(k,y+1));
}
}
}
return 0;
}