//Matrix (2D Grid)

int[][] grid = {{0, 0, 0, 0},

{1, 1, 0, 0},

{0, 0, 0, 1},

{0, 1, 0, 0}};

// Shortest path from top left to bottom right

public int bfs(int[][] grid) {

int ROWS = grid.length;

int COLS = grid[0].length;

int[][] visit = new int[ROWS][COLS];

Deque<int[]> queue = new ArrayDeque<>();

queue.add(new int[2]); // Add {0, 0}

visit[0][0] = 1;

int length = 0;

while (!queue.isEmpty()) {

int queueLength = queue.size();

for (int i = 0; i < queueLength; i++) {

int[] pair = queue.poll();

int r = pair[0], c = pair[1];

if (r == ROWS - 1 && c == COLS - 1) {

return length;

}

// We can directly build the four neighbors

int[][] neighbors = {{r, c + 1}, {r, c - 1}, {r + 1, c}, {r - 1, c}};

for (int j = 0; j < 4; j++) {

int newR = neighbors[j][0], newC = neighbors[j][1];

if (Math.min(newR, newC) < 0 || newR == ROWS || newC == COLS

|| visit[newR][newC] == 1 || grid[newR][newC] == 1) {

continue;

}

queue.add(neighbors[j]);

visit[newR][newC] = 1;

}

}

length++;

}

return length; // This should never be called

}

}