Number of Islands

Given a NxN matrix with values X and O where X represent land and O represent water find the number of islands. Two consecutive X X (horizontal or vertical) will be part of single island while diagonal X X are not. (Solve using graph - DFS or BFS with Queue)

 

public class Solution {
        public int numberOfIslands(char[][] m) {
                int count = 0;
                if (m == null || m.length == 0 || m[0].length == 0) {
                    return count;
                }

                for (int i = 0; i < m.length; i++) {
                    for (int j = 0; j < m[0].length; j++) {
                        if (m[i][j] == 'X') {
                            count++;
                            helper(m, i, j);
                        }
                    }
                }
                return count;
        }

        private void helper(char[][] m, int x, int y) {
            if (x < 0 || y < 0 || x >= m.length || y >= m[0].length || m[x][y] == 'L' || m[x][y] == 'O') {
                    return;
            }
            m[x][y] = 'L';
            helper(m, x + 1, y);
            helper(m, x - 1, y);
            helper(m, x, y + 1);
            helper(m, x, y - 1);
        }

        public static void main(String[] args) {
                Solution s = new Solution();
                char[][] m = {
                                {'X', 'X', 'X', 'O', 'O'},
                                {'O', 'O', 'O', 'X', 'X'},
                                {'O', 'O', 'O', 'X', 'X'},
                                {'O', 'O', 'X', 'O', 'O'},
                                {'O', 'O', 'O', 'X', 'X'},
                                {'X', 'O', 'X', 'O', 'O'},
                                {'X', 'X', 'X', 'O', 'O'}
                                };
                System.out.println(s.numberOfIslands(m));
        }
}