Find largest island in a board
1 package fb;
2
3 public class LargestIsland {
4 public int findLargestIsland(int[][] board) {
5 if (board==null || board.length==0 || board[0].length==0) return 0;
6 int m = board.length;
7 int n = board[0].length;
8 int maxArea = 0;
9 for (int i=0; i<m; i++) {
10 for (int j=0; j<n; j++) {
11 if (board[i][j] != 1) continue;
12 int area = 0;
13 area = dfs(board, i, j, m, n);
14 maxArea = Math.max(maxArea, area);
15 }
16 }
17 return maxArea;
18 }
19
20
21 public int dfs(int[][] board, int i, int j, int m, int n) {
22 if (i<0 || i>=m || j<0 || j>=n || board[i][j]!=1) return 0;
23 int area = 1;
24 board[i][j] = 2;
25 area += dfs(board, i-1, j, m, n);
26 area += dfs(board, i+1, j, m, n);
27 area += dfs(board, i, j-1, m, n);
28 area += dfs(board, i, j+1, m, n);
29 return area;
30 }
31
32 /**
33 * @param args
34 */
35 public static void main(String[] args) {
36 // TODO Auto-generated method stub
37 LargestIsland sol = new LargestIsland();
38 //int[][] arr = new int[][]{{1,0,0,0},{0,1,0,0},{0,0,1,1},{0,0,1,1}};
39 int[][] arr = new int[][]{{1,0,1},{0,1,0},{0,1,1}};
40 int res = sol.findLargestIsland(arr);
41 System.out.println(res);
42 }
43
44 }
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