zoukankan      html  css  js  c++  java
  • Java 图的遍历-LeetCode200

    Given a 2d grid map of '1's (land) and '0's (water), count the number of islands. An island is surrounded by water and is formed by connecting adjacent lands horizontally or vertically. You may assume all four edges of the grid are all surrounded by water.

    Example 1:

    11110
    11010
    11000
    00000

    Answer: 1

    Example 2:

    11000
    11000
    00100
    00011

    Answer: 3

    大意就是给个图,找寻所有的子图。注意两点:1.该二维数组并不一定是方阵;2.数组有可能是空的情况

    代码如下:

     1 public class Solution {
     2     class pos {
     3         public int x;
     4         public int y;
     5 
     6         public pos(int x, int y) {
     7             this.x = x;
     8             this.y = y;
     9         }
    10     }
    11 
    12     public int numIslands(char[][] grid) {
    13         if (grid.length == 0)
    14             return 0;
    15         int count = 0;
    16         int xl = grid.length, yl = grid[0].length;
    17         int[][] visit = new int[xl][yl];
    18         LinkedList<pos> lp = new LinkedList<Solution.pos>();
    19         pos cur;
    20         for (int i = 0; i < xl; i++) {
    21             for (int j = 0; j < yl; j++) {
    22                 if (grid[i][j] == '0')
    23                     continue;
    24                 if (grid[i][j] == '1' && visit[i][j] == 1)
    25                     continue;
    26                 cur = new pos(i, j);
    27                 lp.push(cur);
    28                 while (lp.size() > 0) {
    29                     cur = lp.poll();
    30                     visit[cur.x][cur.y] = 1;
    31                     if (cur.x + 1 < xl && grid[cur.x + 1][cur.y] == '1'
    32                             && visit[cur.x + 1][cur.y] != 1) {
    33                         lp.push(new pos(cur.x + 1, cur.y));
    34                     }
    35                     if (cur.x - 1 >= 0 && grid[cur.x - 1][cur.y] == '1'
    36                             && visit[cur.x - 1][cur.y] != 1) {
    37                         lp.push(new pos(cur.x - 1, cur.y));
    38                     }
    39                     if (cur.y + 1 < yl && grid[cur.x][cur.y + 1] == '1'
    40                             && visit[cur.x][cur.y + 1] != 1) {
    41                         lp.push(new pos(cur.x, cur.y + 1));
    42                     }
    43                     if (cur.y - 1 >= 0 && grid[cur.x][cur.y - 1] == '1'
    44                             && visit[cur.x][cur.y - 1] != 1) {
    45                         lp.push(new pos(cur.x, cur.y - 1));
    46                     }
    47                 }
    48                 ++count;
    49             }
    50         }
    51 
    52         return count;
    53     }
    54 
    55     public static void main(String[] args) {
    56         char[][] grid1 = { { '1', '1', '1', '1', '0' },
    57                 { '1', '1', '0', '1', '0' }, { '1', '1', '0', '0', '0' },
    58                 { '0', '0', '0', '0', '0' } }, grid2 = {
    59                 { '1', '1', '0', '0', '0' }, { '1', '1', '0', '0', '0' },
    60                 { '0', '0', '1', '0', '0' }, { '0', '0', '0', '1', '1' } }, grid3 = {
    61                 { '1', '1', '1' }, { '0', '1', '0' }, { '1', '1', '1' } };
    62         Solution s = new Solution();
    63         System.out.println(s.numIslands(grid1));
    64         System.out.println(s.numIslands(grid2));
    65         System.out.println(s.numIslands(grid3));
    66     }
    67 }

    我利用的是广度优先遍历,也可尝试深度优先遍历

  • 相关阅读:
    火狐下button标签子元素无法点击
    js里面的this指向
    (转载)http协议的Request Payload 和 Form Data 的区别
    (转载)http压缩 Content-Encoding: gzip
    函数的length属性
    Expires
    Etag 和 If-None-Match
    Mac下升级node到最新版本
    高级函数之函数绑定
    Java数据结构和算法day01 稀疏数组与队列
  • 原文地址:https://www.cnblogs.com/xlturing/p/4412932.html
Copyright © 2011-2022 走看看