2014 UESTC Training for Search Algorithm Problem D 方老师与素数
2014-05-05 16:42
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BFS 水题。
先筛一下素数就好。
先筛一下素数就好。
//方老师与素数 #include<cstdio> #include<cstring> #include<algorithm> #include<queue> using namespace std; bool prime[10001]; bool vis[10001]; int n,m; int bfs() { queue<int>q; q.push(n); q.push(-1); int ans=0; while(!q.empty()) { int tmp=q.front(); if(tmp==-1) { q.pop(); if(q.empty()) return -1; ans++; q.push(tmp);continue; }q.pop(); if(tmp==m)return ans; int s; for(int i=1;i<=9;i++) { s=tmp%1000+i*1000; if(!vis[s]&&!prime[s]) vis[s]=1,q.push(s); } for(int i=0;i<=9;i++) { s=tmp/1000*1000+tmp%100+i*100; if(!vis[s]&&!prime[s]) vis[s]=1,q.push(s); } for(int i=0;i<=9;i++) { s=tmp/100*100+tmp%10+i*10; if(!vis[s]&&!prime[s]) vis[s]=1,q.push(s); } for(int i=0;i<=9;i++) { s=tmp/10*10+i; if(!vis[s]&&!prime[s]) vis[s]=1,q.push(s); } } return -1; } int main() { prime[1]=1; for(int i=2;i<10001;i++) for(int j=2;i*j<10001;j++) prime[i*j]=1; int t; scanf("%d",&t); while(t--) { scanf("%d%d",&n,&m); memset(vis,0,sizeof(vis)); int tmp=bfs(); if(tmp==-1) puts("Impossible"); else printf("%d\n",tmp); } }
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