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// 1091. Shortest Path in Binary Matrix
#include <assert.h>
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
/*
* given an n x n binary matrix 'grid', return the length of the shortest clear
* path in the matrix. if there is no clear path, return -1. a clear path in a
* binary matrix is a path from the top-left cell (ie. 0,0) to the bottom-right
* cell (ie. n - 1, n - 1) such thatyt
* - all the visited cells are of the path 0
* - all the adjacent cells of the path are 8-directionally connected (ie. they
* are different and they share an edge of a corner) the length of a clear path
* is the number of visited cells of this path
*/
typedef struct pair {
int x;
int y;
} pair_t;
typedef pair_t queue_data_t;
typedef enum queue {
QUEUE_OK,
QUEUE_EMPTY,
QUEUE_FULL,
QUEUE_ERROR = 0xFF
} queue_er_em;
typedef struct queue_t {
queue_data_t *value;
int buf_size;
int offer_i;
int poll_i;
int cnt;
} queue_t;
queue_t *create_queue(int buf_size) {
queue_t *q = malloc(sizeof(queue_t));
memset(q, 0, sizeof(queue_t));
q->buf_size = buf_size;
q->value = malloc(buf_size * sizeof(queue_data_t));
memset(q->value, 0, buf_size * sizeof(queue_data_t));
return q;
}
queue_er_em offer_queue(queue_t *q, queue_data_t *data) {
assert(q->cnt < q->buf_size);
if (q->cnt >= q->buf_size)
return QUEUE_ERROR;
memcpy(&q->value[q->offer_i++], data, sizeof(queue_data_t));
if (q->offer_i == q->buf_size)
q->offer_i = 0;
q->cnt++;
return QUEUE_OK;
}
queue_er_em poll_queue(queue_t *q, queue_data_t *data) {
assert(q->cnt);
if (q->cnt < 1)
return QUEUE_EMPTY;
memcpy(data, &q->value[q->poll_i++], sizeof(queue_data_t));
if (q->poll_i == q->buf_size)
q->poll_i = 0;
q->cnt--;
return QUEUE_OK;
}
inline int get_data(queue_t *q) { return q->cnt; }
bool empty(queue_t *q) { return (q->cnt); }
int shortestPathBinaryMatrix(int **grid, int grid_size, int *grid_col_size) {
if (grid[0][0] == 1)
return -1;
queue_t *buf = create_queue(500);
int dirr[8][2] = {{-1, -1}, {-1, 0}, {-1, 1}, {0, -1},
{0, 1}, {1, -1}, {1, 0}, {1, 1}};
pair_t p = {.x = 0, .y = 0};
pair_t tmp;
int cnt = 0;
offer_queue(buf, &p);
while (!empty(buf)) {
int c = get_data(buf);
cnt++;
for (int i = 0; i < c; i++) {
poll_queue(buf, &p);
if (p.x == grid_size - 1 && p.y == grid_col_size[0] - 1)
return cnt;
for (int j = 0; j < 8; j++) {
int tr = p.x + dirr[j][0];
int tc = p.y + dirr[j][1];
if (tr >= 0 && tr < grid_size && tc >= 0 && tc < grid_col_size[0] &&
!grid[tr][tc]) {
tmp.x = tr;
tmp.y = tc;
offer_queue(buf, &tmp);
grid[tr][tc] = -1;
}
}
}
}
return -1;
}
int main() int g1[2][2] = {{0, 1}, {1, 0}}, gs1 = 2, gcs1[] = { 2, 2 };
int g2[3][3] = {{0, 0, 0}, {1, 1, 0}, {1, 1, 1}}, gs2 = 3, gcs[] = {3, 3, 3};
int g3[3][3] = {{1, 0, 0}, {1, 1, 0}, {1, 1, 0}}, gs3 = 3, gc3[] = {3, 3, 3};
printf("%d\n", shortestPathBinaryMatrix(g1, gs1, gc1)); // expect: 2
printf("%d\n", shortestPathBinaryMatrix(g2, gs2, gc2)); // expect: 4
printf("%d\n", shortestPathBinaryMatrix(g3, gs3, gc3)); // expect: -1
}
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