FB面经 Prepare: Count Unique Island

 

数unique island, 比如

110000

110001

001101

101100

100000

总共两个unique岛，不是四个

方法可以是记录每次新的岛屿搜索的路径，left,right,up,down, 作为标志是否相同的key，存hashset

 

package fbOnsite;
import java.util.*;
public class UniqueIsland {
    public int countIsland(int[][] grid) {
        HashSet<String> set = new HashSet<String>();
        
        for (int i=0; i<grid.length; i++) {
            for (int j=0; j<grid[0].length; j++) {
                if (grid[i][j] != 1) continue;
                StringBuilder path = new StringBuilder();
                dfs(grid, i, j, path.append('s')); //start
                set.add(path.toString());
            }
        }
        
        for(String str : set) {
            System.out.println(str);
        }
        
        return set.size();
    }
    
    public void dfs(int[][] grid, int i, int j, StringBuilder sb) {
        grid[i][j] = 2;
        //up
        if (i>=1 && grid[i-1][j]==1) dfs(grid, i-1, j, sb.append('u'));
        //right
        if (j<grid[0].length-1 && grid[i][j+1]==1) dfs(grid, i, j+1, sb.append('r'));
        //down
        if (i<grid.length-1 && grid[i+1][j]==1) dfs(grid, i+1, j, sb.append('d'));
        //left
        if (j>=1 && grid[i][j-1]==1) dfs(grid, i, j-1, sb.append('l'));
    }

    /**
     * @param args
     */
    public static void main(String[] args) {
        // TODO Auto-generated method stub
        UniqueIsland sol = new UniqueIsland();
        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}};
        int res = sol.countIsland(grid);
        System.out.println(res);
    }

}