zoukankan      html  css  js  c++  java
  • LeetCode 694. Number of Distinct Islands

    原题链接在这里:https://leetcode.com/problems/number-of-distinct-islands/description/

    题目:

    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.

    Note: The length of each dimension in the given grid does not exceed 50.

    题解:

    对每个为1的点进行dfs, 同时记下做过的path. 看最后做过多少种不同的path.

    Note: dfs每层最后要加分割的数字, 不然不能确定step是在哪个level走的. 

    e.g. 1-1-1    和  1-1       如果不加分割数字走出的path是相同的.

          |                |

             1            1- 1 

    Time Complexity: O(m*n). m = grid.length. n = grid[0].length.

    Space: O(m*n). stack space.

    AC Java:

     1 class Solution {
     2     public int numDistinctIslands(int[][] grid) {
     3         if(grid == null || grid.length == 0 || grid[0].length == 0){
     4             return 0;
     5         }
     6         
     7         HashSet<List<Integer>> shapes = new HashSet<List<Integer>>();
     8         for(int i = 0; i<grid.length; i++){
     9             for(int j = 0; j<grid[0].length; j++){
    10                 if(grid[i][j] == 1){
    11                     List<Integer> shape = new ArrayList<Integer>();
    12                     dfs(grid, i, j, shape, 0);
    13                     shapes.add(shape);
    14                 }
    15             }
    16         }
    17         
    18         return shapes.size();
    19     }
    20     
    21     private void dfs(int[][] grid, int i, int j, List<Integer> shape, int direction){
    22         if(i<0 || i>=grid.length || j<0 || j>=grid[0].length || grid[i][j]!=1){
    23             return;
    24         }
    25         
    26         grid[i][j] = 0;
    27         shape.add(direction);
    28         dfs(grid, i-1, j, shape, 1);
    29         dfs(grid, i+1, j, shape, 2);
    30         dfs(grid, i, j-1, shape, 3);
    31         dfs(grid, i, j+1, shape, 4);
    32         
    33         shape.add(0);
    34     }
    35 }

    类似Number of Islands.

  • 相关阅读:
    php自动保存文章内容中的图片
    javascript中字符串操作函数
    iis 301永久重定向图文教程
    ORA27101,ORA27102 错误解决方法
    IIS中启用Gzip压缩传输网页方法
    asp.net抓取163邮箱联系人实现代码
    windows IIS 日志文件如何查看及分析
    输出页面所有HTML 包括 JS 添加 的内容
    VS2005无法启动调试 及 解决办法
    Json转行DataTable
  • 原文地址:https://www.cnblogs.com/Dylan-Java-NYC/p/7927002.html
Copyright © 2011-2022 走看看