POJ 1753 Flip Game 棋盘状态搜索

/**
* @Author: Hallbow
* @Date:   2016-07-22T11:04:59+08:00
* @Email:  812966736@qq.com
* @Last modified by:   Hallbow
* @Last modified time: 2016-08-01T11:01:02+08:00
*/
#include <stdio.h>
#define INF 0xFFFFFF

bool 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];
}

// dfs
void 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;
}