994-Rotting-Oranges.java

class Solution {

    public int orangesRotting(int[][] grid) {
        int m = grid.length, n = grid[0].length;
        Queue<int[]> queue = new LinkedList<>();
        int fresh = 0;

        for (int i = 0; i < m; i += 1) {
            for (int j = 0; j < n; j += 1) {
                if (grid[i][j] == 2) queue.offer(new int[] { i, j }); else if (
                    grid[i][j] == 1
                ) fresh += 1;
            }
        }

        int count = 0;
        int[][] dirs = { { 1, 0 }, { -1, 0 }, { 0, 1 }, { 0, -1 } };
        while (!queue.isEmpty() && fresh != 0) {
            count += 1;
            int sz = queue.size();
            for (int i = 0; i < sz; i += 1) {
                int[] rotten = queue.poll();
                int r = rotten[0], c = rotten[1];
                for (int[] dir : dirs) {
                    int x = r + dir[0], y = c + dir[1];
                    if (0 <= x && x < m && 0 <= y && y < n && grid[x][y] == 1) {
                        grid[x][y] = 2;
                        queue.offer(new int[] { x, y });
                        fresh -= 1;
                    }
                }
            }
        }
        return fresh == 0 ? count : -1;
    }
}