FB面經 Prepare: Count Unique Island

 

數unique island, 好比

110000

110001

001101

101100

100000

總共兩個unique島，不是四個

方法能夠是記錄每次新的島嶼搜索的路徑，left,right,up,down, 做爲標誌是否相同的key，存hashset

 

 1 package fbOnsite;
 2 import java.util.*;
 3 public class UniqueIsland {
 4     public int countIsland(int[][] grid) {
 5         HashSet<String> set = new HashSet<String>();
 6         
 7         for (int i=0; i<grid.length; i++) {
 8             for (int j=0; j<grid[0].length; j++) {
 9                 if (grid[i][j] != 1) continue;
10                 StringBuilder path = new StringBuilder();
11                 dfs(grid, i, j, path.append('s')); //start
12                 set.add(path.toString());
13             }
14         }
15         
16         for(String str : set) {
17             System.out.println(str);
18         }
19         
20         return set.size();
21     }
22     
23     public void dfs(int[][] grid, int i, int j, StringBuilder sb) {
24         grid[i][j] = 2;
25         //up
26         if (i>=1 && grid[i-1][j]==1) dfs(grid, i-1, j, sb.append('u'));
27         //right
28         if (j<grid[0].length-1 && grid[i][j+1]==1) dfs(grid, i, j+1, sb.append('r'));
29         //down
30         if (i<grid.length-1 && grid[i+1][j]==1) dfs(grid, i+1, j, sb.append('d'));
31         //left
32         if (j>=1 && grid[i][j-1]==1) dfs(grid, i, j-1, sb.append('l'));
33     }
34 
35     /**
36      * @param args
37      */
38     public static void main(String[] args) {
39         // TODO Auto-generated method stub
40         UniqueIsland sol = new UniqueIsland();
41         int[][] grid = new int[][]{{1,1,0,0,0,0},{1,1,0,0,0,1},{0,0,1,1,0,0},{1,0,1,1,0,0,},{1,0,0,0,0,0}};
42         int res = sol.countIsland(grid);
43         System.out.println(res);
44     }
45 
46 }