牛客 Flip Game

#include<iostream>
#include<cstring>
#include<algorithm>
#include<cstdio>
using namespace std;
const int ax[5] = {0, -1, 1, 0, 0};
const int ay[5] = {0, 0, 0, -1, 1};
char maze[10][10], back[10][10];
void turn(int x, int y) {
    for(int i = 0; i < 5; i++) {
        int tempx = x + ax[i];
        int tempy = y + ay[i];
        if(tempx >= 0 && tempx < 4 && tempy >= 0 && tempy < 4)
        	maze[tempx][tempy] ^= 1;
    }
}
int solve() {
	int ans = 0x3f3f3f3f;
	for (int i = 0; i <= 2 << 4; ++i) {
		memcpy(back, maze, sizeof maze);
		int now = 0;
		for (int j = 0; j < 4; ++j) {
			if (i >> j & 1) {
				now++;
				turn(0, j);
			}
		}
		for (int k = 0; k < 3; ++k)
			for (int l = 0; l < 4; ++l)
				if (maze[k][l] == '0') {
					turn(k + 1, l);
					now++;
				}
		int flag = 1;
		for (int j = 0; j < 4; j++) {
			if (maze[3][j] == '0') {
				flag = 0;
				break;
			}
		}
		if (flag) ans = min(ans, now);
		memcpy(maze, back, sizeof back);
	}
	return ans;
}
int main() {
    for(int i = 0; i < 4; i++)
        for(int j = 0; j < 4; j++) {
            char c;
            cin >> c;
            if(c == 'w')   maze[i][j] = '0';
            else    maze[i][j] = '1';
        }
    int ans = solve();
    for(int i = 0; i < 4; i++)
        for(int j = 0; j < 4; j++)
            if(maze[i][j] == '0')   maze[i][j] = '1';
            else    maze[i][j] = '0';
    ans = min(ans, solve());
    if(ans == 0x3f3f3f3f)    puts("Impossible");
    else    printf("%d\n", ans);
    return 0;
}