[USACO] The Clocks [位操作 BFS]

来源：互联网发布：淘宝开店怎样上传宝贝编辑：程序博客网时间：2024/06/03 22:58

思路：

位操作+广搜。

1到9个时钟，每个时钟状态用两位表示 ,共18位。即每个状态用一个int表示即可。

然后直接广搜，每个状态都是一个int型，每次某状态到达用一个hash表记录。

一次AC。

位操作写得很蛋疼，事后查了一下网上报告，好像没这么做的，就记录一下把。

/*ID:wuyanyi1PROG:clocksLANG:C++*/#include<iostream>#include<fstream>#include<map>#include<vector>#include<string>#include<memory.h>#include<algorithm>#include<queue>#define Min(a,b) (a<b?a:b)#define Max(a,b) (a>b?a:b)#define llong long long intusing namespace std;const int N=10,inf=(1<<30);const int M=(1<<18)-1;int n;int mp[N][N]={{},{4,1,2,4,5},{3,1,2,3},{4,2,3,5,6},{3,1,4,7},{5,2,4,5,6,8},{3,3,6,9},{4,4,5,7,8},{3,7,8,9},{4,5,6,8,9}};int a[N];int vis[M+10];int val[M+10];int chbit(int state,int pos,int bit){if(bit){unsigned int now=1;now<<=pos;state|=now;}else{unsigned int now=M-1;now=(now<<pos)|(now>>(18-pos));state&=now;}return state&M;}int oper(int state,int k){for(int i=1;i<=mp[k][0];i++){int pos=(9-mp[k][i])*2;int now=(state>>pos)&1;//printf("%d ",now);now+=((state>>(pos+1))&1)*2;//printf("%d %d\n",now,pos);if(now==3){state=chbit(state,pos,0);state=chbit(state,pos+1,0);}else{now++;state=chbit(state,pos,now&1);state=chbit(state,pos+1,(now>>1)&1);}}return state&M;}void bfs(int s){queue<int> que;que.push(s);vis[s]=-1;while(!que.empty()){int now=que.front();que.pop();for(int i=1;i<=9;i++){int t=oper(now,i);if(!vis[t]){que.push(t);vis[t]=now;val[t]=i;if(!t){return;}}}}}void print(int i){if(vis[i]!=-1){print(vis[i]);printf("%d",val[i]);if(i)  printf(" ");else  printf("\n");}/*else{printf("",val[i]);}*/}int main(){int s=0;freopen("clocks.in","r",stdin);freopen("clocks.out","w",stdout);for(int i=1;i<=9;i++){scanf("%d",a+i);a[i]/=3;a[i]%=4;//printf("%d",a[i]);s<<=2;s|=a[i];}bfs(s);print(0);//printf("\n");return 0;}