// 1284. Minimum Number of Flips to Convert Binary Matrix to Zero Matrix #include "leetcode.h" /* * given an 'm x n' binary matrix 'mat'. in one step, you can choose one cell * and flip it and all the four neighbours of it if they exist (fip is changing * 1 to 0, and 0 to 1). a pair ofcells are called neighbours if their share one * edge. return the minimum number of steps required to convert 'mat' to a zero * matrix or -1 if you cannot. a binary matrix isa matrix with all cells equal * to 0 or 1 only. a zero matrix is a matrix with all cells equal to 0. */ struct queue_node { int state; int step; }; void push(struct queue_node q[], int *tail, int state, int step) { q[*tail].state = state; q[*tail].step = step; (*tail)++; } int pop_state(struct queue_node q[], int *head) { (*head)++; return q[*head].state; } int pop_step(struct queue_node q[], int *head) { return q[*head].step; } int minFlips(int **mat, int matSize, int *matColSize) { int n = matSize, m = *matColSize, start = 0, head = -1, tail = 0; int dx[5] = {0, 0, 1, 0, -1}; int dy[5] = {0, 1, 0, -1, 0}; struct queue_node *q = (struct queue_node *)malloc((1 << (n * m)) * sizeof(struct queue_node)); for (int i = 0; i < n; i++) for (int j = 0; j < m; j++) if (mat[i][j]) start += 1 << (j + i * m); if (!start) return 0; bool *occur = (bool *)calloc(1, (1LL << (n * m)) * sizeof(bool)); occur[start] = true; push(q, &tail, start, 0); while (head + 1 < tail) { int curr_state = pop_state(q, &head); int curr_step = pop_step(q, &head); for (int i = 0; i < n; i++) { for (int j = 0; j < m; j++) { int new_state = curr_state; for (int k = 0; k < 5; k++) { int nx = i + dx[k]; int ny = j + dy[k]; if (nx >= 0 && nx < n && ny >= 0 && ny < m) new_state ^= 1 << (ny + nx * m); } if (!new_state) { free(q), free(occur); return curr_step + 1; } else if (!occur[new_state]) { occur[new_state] = true; push(q, &tail, new_state, curr_step + 1); } } } } free(q), free(occur); return -1; } int main() { int m1i[2][2] = {{0, 0}, {0, 1}}, m2i[1][1] = {{0}}, m3i[2][3] = {{1, 0, 0}, {1, 0, 0}}; struct two_d_arr m1, m2, m3; two_d_arr_init(&m1, 2, 2, m1i); two_d_arr_init(&m2, 1, 1, m2i); two_d_arr_init(&m3, 2, 3, m3i); printf("%d\n", minFlips(m1.arr, m1.row_size, m1.col_size)); // expect: 3 printf("%d\n", minFlips(m2.arr, m2.row_size, m2.col_size)); // expect: 0 printf("%d\n", minFlips(m3.arr, m3.row_size, m3.col_size)); // expect: -1 two_d_arr_free(&m1); two_d_arr_free(&m2); two_d_arr_free(&m3); }