POJ 1753 Flip Game 棋盘状态搜索

按规则翻转棋子的模拟题。也是一道搜索题。

题意：给出一个棋盘的初始状态，翻动一粒棋子会使得翻动的棋子和周围东南西北四个方向上的棋子也会翻转。black to white , white to black

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传送门：POJ-1753-Flip Game

/*** @Author: Hallbow* @Date:   2016-07-22T11:04:59+08:00* @Email:  [e-mail]* @Last modified by:   Hallbow* @Last modified time: 2016-08-01T11:01:02+08:00*/#include <stdio.h>#define INF 0xFFFFFFbool map[4][4] = {0};bool vis[4][4] = {0};int minSteps = INF;// 是否已全白全黑bool checkMap(){    for(int i=0; i<4; i++){        for(int j=0; j<4; j++){            if(map[i][j] != map[0][0]){                return false;            }        }    }    return true;}// 翻转(x,y)void converseMap(int x, int y){    if(x > 0) map[x-1][y] = !map[x-1][y];    if(x < 3) map[x+1][y] = !map[x+1][y];    if(y > 0) map[x][y-1] = !map[x][y-1];    if(y < 3) map[x][y+1] = !map[x][y+1];    map[x][y] = !map[x][y];}// dfsvoid dfs(int x, int y, int steps){    // 若已到第四行 check是否胜利    if(x == 4){        if(checkMap()){            if(steps < minSteps) minSteps = steps;        }        return;    }    int i,j;    // 翻    converseMap(x, y);    // 换行    if(y == 3){        // 下个棋子        dfs(x+1, 0, steps+1);        // 回溯 不翻        converseMap(x, y);        // 下一棋子        dfs(x+1, 0, steps);    }else{        dfs(x, y+1, steps+1);        converseMap(x, y);        dfs(x, y+1, steps);    }}int main(){    int i,j;    char _map[5];    // freopen("data.in", "r", stdin);    while(1){        minSteps = INF;        for(i=0; i<4; i++){            if(scanf("%s", _map) == EOF) return 0;            for(j=0; _map[j]; j++){                map[i][j] = _map[j] == 'b' ? true: false;            }        }        dfs(0, 0, 0);        if(minSteps != INF){            printf("%d\n", minSteps);        }else{            printf("Impossible\n");        }    }    return 0;}