zoukankan      html  css  js  c++  java
  • [LC] 694. Number of Distinct Islands

    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.

    class Solution {
        int gRow;
        int gCol;
        public int numDistinctIslands(int[][] grid) {
            Set<String> set = new HashSet<>();
            gRow = grid.length;
            gCol = grid[0].length;
            for (int i = 0; i < gRow; i++) {
                for (int j = 0; j < gCol; j++) {
                    if (grid[i][j] == 1) {
                        StringBuilder sb = new StringBuilder();
                        dfs(i, j, sb, "o", grid);
                        set.add(sb.toString());
                    }
                }
            }
            return set.size();
        }
        
        private void dfs(int row, int col, StringBuilder sb, String dir, int[][] grid) {
            if (row < 0 || row >= gRow || col < 0 || col >= gCol || grid[row][col] == 0) {
                return;
            }
            grid[row][col] = 0;
            sb.append(dir);
            dfs(row + 1, col, sb, "r", grid);
            dfs(row - 1, col, sb, "l", grid);
            dfs(row, col + 1, sb, "u", grid);
            dfs(row, col - 1, sb, "d", grid);
            // need to declarative backtrack
            sb.append("b");
        }
    }
  • 相关阅读:
    iOS MJRefresh的使用 (列表上拉加载更多)
    iOS 后台任务
    ios Alamofire网络插件的使用
    springboot shiro ehcache redis 简单使用
    android BottomNavigationView 简单使用
    iOS ksyhttpcache音视频缓存
    springboot 简单使用shiro登录
    springboot 使用 mybatis + mapper
    [LeetCode] Permutations
    【经典算法】回溯算法
  • 原文地址:https://www.cnblogs.com/xuanlu/p/12701442.html
Copyright © 2011-2022 走看看