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);
     }

 }