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  • [leedcode 200] Number of Islands

    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

    public class Solution {
        public int numIslands(char[][] grid) {
            //dfs思想,当发现一个节点是1时,需要将跟其相邻的所有节点置为0,此种方法会改变原grid的值
            if(grid==null||grid.length<=0) return 0;
            int row=grid.length;
            int col=grid[0].length;
            int count=0;
            for(int i=0;i<row;i++){
                for(int j=0;j<col;j++){
                    if(grid[i][j]=='1'){
                        count++;
                        dfs(grid,i,j);
                    }
                }
            }
            return count;
        }
        public void dfs(char[][] grid,int i,int j){
            if(i<0||i>grid.length-1||j<0||j>grid[0].length-1) return;
            if(grid[i][j]=='1'){
                grid[i][j]='0';
                dfs(grid,i-1,j);
                dfs(grid,i+1,j);
                dfs(grid,i,j-1);
                dfs(grid,i,j+1);
            }
        }
    }
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  • 原文地址:https://www.cnblogs.com/qiaomu/p/4700437.html
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