leetcode

1284.cpp (1163B)

 class Solution {
   public:
     int minFlips(const vector<vector<int>> &mat) const {
         static const int offset[] = {-1, 0, 1, 0, -1};
         const int n = size(mat), m = size(mat[0]);
         unsigned res = -1;
 
         const auto valid = [&](int x, int y) { return x >= 0 && x < n && y >= 0 && y < m; };
 
         for (unsigned mask = 0; mask < 1 << (n * m); mask++) {
             auto grid = mat;
 
             for (unsigned k = 0, crnt = mask; crnt; crnt >>= 1, k++) {
                 if (!(crnt & 1)) continue;
 
                 const int a = k / m, b = k % m;
                 for (int k = 0; k < 4; k++) {
                     const int x = a + offset[k + 1];
                     const int y = b + offset[k];
 
                     if (!valid(x, y)) continue;
                     grid[x][y] = !grid[x][y];
                 }
                 grid[a][b] = !grid[a][b];
             }
 
             for (int i = 0; i < n; i++) {
                 for (int j = 0; j < m; j++) {
                     if (grid[i][j]) goto next;
                 }
             }
 
             res = min(res, (unsigned)popcount(mask));
         next:;
         }
 
         return res;
     }
 };