Find Largest Island - Solved

    static Integer max_island_size(ArrayList<ArrayList<Integer>> grid) {
        int nr = grid.size();
        int nc = grid.get(0).size();

        int[][] visited = new int[nr][nc];

        int max_size = 0;
        for (int i = 0; i < nr; i++) {
            for (int j = 0; j < nc; j++) {
                if (visited[i][j] == 0 && grid.get(i).get(j) == 1) {
                    int curr_size = bfs(i, j, visited, grid);
                    max_size = Math.max(max_size, curr_size);
                }
            }
        }

        return max_size;
    }

    static int bfs(int i, int j, int[][] visited, ArrayList<ArrayList<Integer>> grid) {
        int nr = grid.size();
        int nc = grid.get(0).size();

        int count = 1;
        Queue<int[]> q = new LinkedList<int[]>();
        q.offer(new int[]{i,j});
        visited[i][j] = 1;
        while (!q.isEmpty()) {
            int[] curr = q.poll();
            for (int[] neighbor : list_of_neighbors(curr[0], curr[1], grid)) {
                if (visited[neighbor[0]][neighbor[1]] == 0) {
                    q.offer(neighbor);
                    visited[neighbor[0]][neighbor[1]] = 1;
                    count++;
                }
            }
        }

        return count;
    }

    static ArrayList<int[]> list_of_neighbors(int i, int j, ArrayList<ArrayList<Integer>> grid) {
        int nr = grid.size();
        int nc = grid.get(0).size();

        ArrayList<int[]> neighbors = new ArrayList<int[]>();

        if (i - 1 >= 0 && i - 1 <= nr - 1 && grid.get(i - 1).get(j) == 1) {
            neighbors.add(new int[]{i - 1, j});
        }

        if (i + 1 >= 0 && i + 1 <= nr - 1 && grid.get(i + 1).get(j) == 1) {
            neighbors.add(new int[]{i + 1, j});
        }

        if (j - 1 >= 0 && j - 1 <= nc - 1 && grid.get(i).get(j - 1) == 1) {
            neighbors.add(new int[]{i, j - 1});
        }

        if (j + 1 >= 0 && j + 1 <= nc - 1 && grid.get(i).get(j + 1) == 1) {
            neighbors.add(new int[]{i, j + 1});
        }

        return neighbors;
    }