POJ1753 Flip Game

#include<iostream>
using namespace std;

int arr[5];//黑色状态 
int brr[5];//白色状态 
char ch;
int ans = 1e9 + 7;

int sum (int x) {
    int ans = 0;
    while (x) {
        if (x & 1) ans++;
        x >>= 1;
    }
    return ans;
}

void solved (int a[]) {
    int crr[5];
    int cnt = 0;
    for (int i = 0; i <= ((1 << 4) - 1); i++) {//枚举第一行2^4种翻转情况，用01序列代表黑白情况 
        cnt = sum(i);
        crr[0] = a[0] ^ i ^ (i >> 1) ^ ((i << 1) & ((1 << 4) - 1));
        crr[1] = a[1] ^ i;
        for (int j = 1; j < 4; j++) {
            int tt = crr[j - 1];
            cnt += sum(tt);
            crr[j] = crr[j] ^ tt ^ (tt >> 1) ^ ((tt << 1) & ((1 << 4) - 1));
            crr[j + 1] = a[j + 1] ^ tt;
        }
        if (crr[3] == 0) ans = min(ans, cnt);//若最后一行所有都是同一种颜色，即为正确方案 
    }
}

int main() {
    for (int i = 0; i < 4; i++) {
        for (int j = 0; j < 4; j++) {
            cin >> ch;
            if (ch == 'b') arr[i] |= (1 << j);
            else brr[i] |= (1 << j);
        }
    }
    solved(arr);
    solved(brr);
    if (ans > 16) cout << "Impossible" << "\n";
    else cout << ans << "\n";

    return 0;
}