[LeetCode-JAVA] Number of Islands

標籤：

題目：

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

思路： 迴圈遍曆數組，發現一個1就將其左右上下相連的所有1都找到 並且標記，同時計數器加1即可。

代碼：

public class Solution {    public int numIslands(char[][] grid) {        int m = grid.length;        if(m == 0) return 0;        int n = grid[0].length;                int count = 0;        for(int i = 0 ; i < m ; i++){            for(int j = 0 ; j < n ; j++){                if(grid[i][j] == ‘1‘){                    replace(grid, i, j);                    count++;                }            }        }        return count;    }    public void replace(char[][] grid, int i, int j){        int m = grid.length;        int n = grid[0].length;                grid[i][j] = ‘#‘;        if(j-1 >= 0 && grid[i][j-1] == ‘1‘)            replace(grid, i, j-1);        if(i-1 >= 0 && grid[i-1][j] == ‘1‘)            replace(grid, i-1, j);        if(i+1 < m && grid[i+1][j] == ‘1‘)            replace(grid, i+1, j);        if(j+1 < n && grid[i][j+1] == ‘1‘)            replace(grid, i, j+1);                return;    }}

 

[LeetCode-JAVA] Number of Islands