FB面经 Prepare: Largest Island

Find largest island in a board

package fb;

public class LargestIsland {
    public int findLargestIsland(int[][] board) {
        if (board==null || board.length==0 || board[0].length==0) return 0;
        int m = board.length;
        int n = board[0].length;
        int maxArea = 0;
        for (int i=0; i<m; i++) {
            for (int j=0; j<n; j++) {
                if (board[i][j] != 1) continue;
                int area = 0;
                area = dfs(board, i, j, m, n);
                maxArea = Math.max(maxArea, area);
            }
        }
        return maxArea;
    }
    
    
    public int dfs(int[][] board, int i, int j, int m, int n) {
        if (i<0 || i>=m || j<0 || j>=n || board[i][j]!=1) return 0;
        int area = 1;
        board[i][j] = 2;
        area += dfs(board, i-1, j, m, n);
        area += dfs(board, i+1, j, m, n);
        area += dfs(board, i, j-1, m, n);
        area += dfs(board, i, j+1, m, n);
        return area;
    }

    /**
     * @param args
     */
    public static void main(String[] args) {
        // TODO Auto-generated method stub
        LargestIsland sol = new LargestIsland();
        //int[][] arr = new int[][]{{1,0,0,0},{0,1,0,0},{0,0,1,1},{0,0,1,1}};
        int[][] arr = new int[][]{{1,0,1},{0,1,0},{0,1,1}};
        int res = sol.findLargestIsland(arr);
        System.out.println(res);
    }

}