POJ 3278 Catch That Cow

注意x等于0的时候就不要减一了,同样x*2大于10W也不行

#include <iostream>#include <cstdio>#include <memory.h>#include <queue>using namespace std;const int maxn=100010;bool vis[maxn];int x,k;struct state{int x,t;state(int xx=0,int tt=0):x(xx),t(tt){}};int bfs(int s){queue<state>q;q.push(state(s,0));vis[s]=1;while (q.size()){state t=q.front();q.pop();if(t.x==k)return t.t;int nx=t.x+1;if(t.x<k&&!vis[nx]){//如果当前x比k大 那没有必要加1vis[nx]=1;q.push(state(nx,t.t+1));}nx=t.x-1;if(nx>=0&&!vis[nx]){//边界vis[nx]=1;q.push(state(nx,t.t+1));}if(t.x<k&&t.x*2<maxn&&!vis[t.x*2]){//如果当前x比k大,没必要乘2vis[t.x*2]=1;q.push(state(t.x*2,t.t+1));}}}int main(){while (scanf("%d%d",&x,&k)==2){memset(vis,0,maxn);printf("%d\n",bfs(x));}return 0;}