[kuangbin带你飞]专题一 简单搜索 - F - Prime Path

 #include<iostream>
 #include<cstdio>
 #include<cstring>
 #include<algorithm>
 #include<queue>
 using namespace std;
 struct node
 {
     int x;
     int s;
 };
 bool prim[];
 bool vis[];
 int chr(int x,int i,int j)
 {
     int b,s = ;
     int tmp = ;
     for(int z = ; z<= ; z++)
     {
         b = x%;
         x/=;
         if(i==z)    b = j;
         tmp+=s*b;
         s*=;
     }
     return tmp;
 }
 int main()
 {
 //    freopen("in.in","r",stdin);
     for(int i = ; i <= ; i++)
     {
         if(prim[i])    continue;
         for(int j = ; j <= /i; j++)
             prim[i*j] = true;
     }
     queue<node>q;
     node s, t;
     int n, a, b, tmp;
     bool flag;
     scanf("%d",&n);
     while(n--)
     {
         flag = false;
         memset(vis,false,sizeof(vis));
         scanf("%d%d",&a,&b);
         s.x = a;
         s.s = ;
         q.push(s);
         while(q.size())
         {
             s = q.front();
             q.pop();
             t.s = s.s + ;
             vis[s.x] = true;
             if(s.x == b)
             {
                 flag = true;
                 break;
             }
             for(int i = ; i <= ; i++)
                 for(int j = ; j <= ; j++)
                 {
                     if(i== && j==)    continue;
                     t.x = chr(s.x,i,j);
                     if(prim[t.x] || vis[t.x])    continue;
                     q.push(t);
                 }
         }
         while(q.size())    q.pop();
         if(flag)    cout<<s.s<<endl;
         else        cout<<"Impossible"<<endl;
     }
     return ;
 }