Q4 Number of Islands - LeetCode 200

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Sat Apr 08 2023 16:24:47 GMT+0000 (Coordinated Universal Time)

Saved by @Ayush_dabas07

class Solution {
    public int numIslands(char[][] grid) {
        /* we treat this like a question of graph to find components which are 
        islands in this case 
        */
        boolean visited[][] = new boolean [grid.length][grid[0].length];
        int component = 0;

        //dfs from every node 
        for(int i = 0 ; i < grid.length ;i++){

            for(int j = 0 ; j < grid[0].length ;j++){
                
                //if it is land and visited is false
                if(grid[i][j] == '1' && visited[i][j] == false){

                    dfs(grid , i , j , visited);
                    
                    component++;
                }
                
            }
        }

        return component;
    }

    public void dfs (char[][]grid , int i , int j , boolean[][] visited){
        
        //base case
        if(i < 0 || j < 0 || i >= grid.length || j >= grid[0].length
        || visited[i][j] == true || grid[i][j] == '0')
        return ;

            visited[i][j] = true;
            
            //going in all 4 directions

            dfs(grid , i , j+1 , visited);
            dfs(grid , i+1 , j , visited);
            dfs(grid , i-1 , j , visited);
            dfs(grid , i , j-1 , visited);
        
    }


}

https://leetcode.com/problems/number-of-islands/

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