dsa/Graphs/NumberOfProvinces.java

import java.util.*;
import java.io.*;

class NumberOfProvinces {

    // DFS
    public static void dfs(int node, boolean visited[], ArrayList<ArrayList<Integer>> adj){
        visited[node] = true;

        for (Integer it: adj.get(node)){
            if (!visited[it]){
                dfs(it, visited, adj);
            }
        }
    }

    //  BFS 
    public static void bfs(int start, boolean visited[], ArrayList<ArrayList<Integer>> adj){
        Queue<Integer> q = new LinkedList<>();

        q.add(start);
        visited[start] = true;

        while(!q.isEmpty()){
            Integer node = q.poll();

            for(Integer it : adj.get(node)){
                if(!visited[it]){
                    visited[it] = true;
                    q.add(it);
                }
            }
        }
    }

    //  PROVINCE COUNT 
    static int numProvinces(int[][] matrix, int V) {

        // convert adjacency matrix -> adjacency list
        ArrayList<ArrayList<Integer>> adj = new ArrayList<>();
        for(int i=0;i<V;i++) adj.add(new ArrayList<>());

        for(int i=0;i<V;i++){
            for(int j=0;j<V;j++){
                if(matrix[i][j] == 1 && i != j){
                    adj.get(i).add(j);
                }
            }
        }

        boolean visited[] = new boolean[V];
        int count = 0;

        for(int i=0;i<V;i++){
            if(!visited[i]){
                count++;

                //  choose one 
                dfs(i, visited, adj);
                // bfs(i, visited, adj);
            }
        }

        return count;
    }


    //  DRIVER 
    public static void main(String[] args) {

        int[][] matrix = {
            {1,0,1},
            {0,1,0},
            {1,0,1}
        };

        int V = matrix.length;

        int ans = numProvinces(matrix, V);
        System.out.println(ans);
    }
}