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// 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);
}
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