poj 1753 Flip Game 二进制状态压缩

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poj 1753 Flip Game

http://poj.org/problem?id=1753

#include <iostream>#include <cstdio>#include <cstring>#include <queue>using namespace std;int bit[18],vis[70000] , value;int mov[5][2]={0, 0, -1, 0, 1, 0, 0, 1, 0, -1};char map[5][5];struct node{    int v , step;};void init(){    int i, j;    value=0 ;    memset(vis, 0, sizeof(vis));    for(i=0 ;i< 4; i++){        for(j=0; j<4; j++){            if(map[i][j]=='b')                value|=bit[i*4+j];        }    }//cout<<"AA"<<value<<endl;    vis[value]=1;}void bfs(){    queue <node > q;    int i , j;    node head, start, next ;    head.v = value;    head.step = 0;    q.push(head);    while(!q.empty()){        int tx, ty, x, y;        head=q.front() ;       // printf("%d  %d \n", head.v, head.step);        q.pop();        if(head.v ==0||head.v ==(0xffff)) {printf("%d\n",head.step);return ;}        next.step = head.step + 1;        for(i=0 ;i< 16; i++){            x=i/4;            y=i%4;            next.v= head.v ;            for(j =0; j<5; j++){                tx=x+mov[j][0];                ty=y+mov[j][1];                if(tx<0 || tx>=4 || ty<0 || ty>=4 ) continue;                next.v ^=bit[tx*4 + ty];            }            if(next.v ==0||next.v ==(0xffff)) {printf("%d\n",next.step);return ;}            if(!vis[next.v]) {                vis[next.v]=1;                q.push(next);            }        }    }    printf("Impossible\n");}int main(){  //  freopen("1.txt", "r", stdin);    int i, j;    for(i=0; i<16; i++){        bit[i]= 1<<i ;//cout<<bit[i]<<" ";    }    while(scanf("%s%s%s%s",map[0], map[1], map[2], map[3] )!=EOF){        init();        bfs();    }    return 0;}