Day-9 Rotting Oranges

class Solution {
    public int orangesRotting(int[][] grid) {
        Queue<Pair<Integer, Integer>> queue = new ArrayDeque();
        // Step 1). build the initial set of rotten oranges
        int freshOranges = 0;
        int ROWS = grid.length, COLS = grid[0].length;

        for (int r = 0; r < ROWS; ++r)
            for (int c = 0; c < COLS; ++c)
                if (grid[r][c] == 2)
                    queue.offer(new Pair(r, c));
                else if (grid[r][c] == 1)
                    freshOranges++;
        //if no freshOranges then no need to iterate
        if ( freshOranges==0) return 0;
        // Step 2). start the rotting process via BFS
        int minutesElapsed = -1;
        int[][] directions = { {-1, 0}, {0, 1}, {1, 0}, {0, -1}};
        while (!queue.isEmpty()) {
            int size=queue.size();
            while(size-->0){
                Pair<Integer, Integer> p = queue.poll();
                int row = p.getKey();
                int col = p.getValue();
                    // this is a rotten orange
                    // then it would contaminate its neighbors
                    for (int[] d : directions) {
                    int neighborRow = row + d[0];
                    int neighborCol = col + d[1];
                    if (neighborRow >= 0 && neighborRow < ROWS && 
                        neighborCol >= 0 && neighborCol < COLS) {
                        if (grid[neighborRow][neighborCol] == 1) {
                            // this orange would be contaminated
                            grid[neighborRow][neighborCol] = 2;
                            freshOranges--;
                            // this orange would then contaminate other oranges
                            queue.offer(new Pair(neighborRow, neighborCol));
                        }
                    }
                }
            }
            
            minutesElapsed++;
        }
        // return elapsed minutes if no fresh orange left
        return freshOranges == 0 ? minutesElapsed : -1;
    }
}