694. Number of Distinct Islands

本文主要是介绍694. Number of Distinct Islands，对大家解决编程问题具有一定的参考价值，需要的程序猿们随着小编来一起学习吧！

Given a non-empty 2D array grid of 0's and 1's, an island is a group of 1's (representing land) connected 4-directionally (horizontal or vertical.) You may assume all four edges of the grid are surrounded by water.

Count the number of distinct islands. An island is considered to be the same as another if and only if one island can be translated (and not rotated or reflected) to equal the other.

Example 1:

11000
11000
00011
00011

Given the above grid map, return 1.

Example 2:

11011
10000
00001
11011

Given the above grid map, return 3.

Notice that:

11
1

and

 1
11

are considered different island shapes, because we do not consider reflection / rotation.

 1 class Solution {
 2     int[][] dirs = new int[][] { { 1, 0 }, { 0, 1 }, { -1, 0 }, { 0, -1 } };
 3     public int numDistinctIslands(int[][] grid) {
 4         Set<String> set = new HashSet<>();
 5         int res = 0;
 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) {
10                     StringBuilder sb = new StringBuilder();
11                     helper(grid, i, j, 0, 0, sb);
12                     String s = sb.toString();
13                     if (!set.contains(s)) {
14                         res++;
15                         set.add(s);
16                     }
17                 }
18             }
19         }
20         return res;
21     }
22 
23     public void helper(int[][] grid, int i, int j, int xpos, int ypos, StringBuilder sb) {
24         grid[i][j] = 0;
25         sb.append(xpos + "" + ypos);
26         for (int[] dir : dirs) {
27             int x = i + dir[0];
28             int y = j + dir[1];
29             if (x < 0 || y < 0 || x >= grid.length || y >= grid[0].length || grid[x][y] == 0)
30                 continue;
31             helper(grid, x, y, xpos + dir[0], ypos + dir[1], sb);
32         }
33     }
34 }

这篇关于694. Number of Distinct Islands的文章就介绍到这儿，希望我们推荐的文章对大家有所帮助，也希望大家多多支持为之网！