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// 1091. Shortest Path in Binary Matrix
#include "leetcode.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
*/
#define MAX_SIZE 100
struct node {
int row;
int col;
int step;
};
struct queue {
struct node n[MAX_SIZE * MAX_SIZE];
int front;
int rear;
};
void queue_init(struct queue *q) {
q->front = -1;
q->rear = -1;
}
bool queue_empty(struct queue *q) { return q->front == -1; }
bool queue_full(struct queue *q) { return q->rear == MAX_SIZE * MAX_SIZE - 1; }
void queue_push(struct queue *q, struct node n) {
if (queue_full(q))
return;
if (queue_empty(q))
q->front = 0;
q->n[++q->rear] = n;
}
struct node queue_pop(struct queue *q) {
struct node n = {0, 0, 0};
if (queue_empty(q))
return n;
n = q->n[q->front++];
if (q->front > q->rear) {
q->front = -1;
q->rear = -1;
}
return n;
}
bool valid(int row, int col, int n, int **grid) {
return row >= 0 && row < n && col >= 0 && col < n && grid[row][col] == 0;
}
int shortestPathBinaryMatrix(int **grid, int gridSize, int *gridColSize) {
if (grid[0][0] == 1)
return -1;
int dir[8][2] = {{0, 1}, {1, 0}, {0, -1}, {-1, 0},
{-1, -1}, {-1, 1}, {1, -1}, {1, 1}};
int n = gridSize;
bool vis[MAX_SIZE][MAX_SIZE] = {false};
struct queue q;
queue_init(&q);
vis[0][0] = true;
struct node start = {0, 0, 1};
queue_push(&q, start);
while (!queue_empty(&q)) {
struct node curr = queue_pop(&q);
if (curr.row == n - 1 && curr.col == n - 1)
return curr.step;
for (int i = 0; i < 8; i++) {
int nr = curr.row + dir[i][0], nc = curr.col + dir[i][1];
if (valid(nr, nc, n, grid) && !vis[nr][nc]) {
vis[nr][nc] = true;
struct node next = {nr, nc, curr.step + 1};
queue_push(&q, next);
}
}
}
return -1;
}
int main() {
int g1i[2][2] = {{0, 1}, {1, 0}};
int g2i[3][3] = {{0, 0, 0}, {1, 1, 0}, {1, 1, 0}};
int g3i[3][3] = {{1, 0, 0}, {1, 1, 0}, {1, 1, 0}};
struct two_d_arr g1, g2, g3;
two_d_arr_init(&g1, 2, 2, g1i);
two_d_arr_init(&g2, 3, 3, g2i);
two_d_arr_init(&g3, 3, 3, g3i);
printf("%d\n", shortestPathBinaryMatrix(g1.arr, g1.row_size,
g1.col_size)); // expect: 2
printf("%d\n", shortestPathBinaryMatrix(g2.arr, g2.row_size,
g3.col_size)); // expect: 4
printf("%d\n", shortestPathBinaryMatrix(g3.arr, g3.row_size,
g3.col_size)); // expect: -1
two_d_arr_free(&g1);
two_d_arr_free(&g2);
two_d_arr_free(&g3);
}
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