Q21 Water Supply In A Village - Coding Ninjas

import java.util.ArrayList;
import java.util.PriorityQueue;

public class Solution {

    public static int supplyWater(int n, int k, int[] wells, int[][] pipes) {
        /* Q21 graph playlist , we add Node 0 , as dummy node which
        acts as our wells edge for each wedge and then we find 
        MST for the whole graph
        */
        
        //making graph of pipes
        ArrayList<ArrayList<pair>> graph = new ArrayList<>();
        
        //initializing AL
        for(int i = 0 ;i <= n ; i++)
        graph.add(new ArrayList<>());

        for(int pipe[] : pipes){
            
            graph.get(pipe[0]).add(new pair(pipe[1],pipe[2]));
            graph.get(pipe[1]).add(new pair(pipe[0],pipe[2]));
        }

        //now adding Wells edge in graph for each vertex
        for(int i = 0 ;i < n ; i++){
            graph.get(i+1).add(new pair(0 , wells[i]));
            graph.get(0).add(new pair(i+1 , wells[i]));
        }

        //now running prims algo for MST 
        PriorityQueue<pair> pq = new PriorityQueue<>();
        pq.add(new pair(0,0));
        boolean visited[] = new boolean[n + 1];

        int ans = 0;
        while(pq.size() > 0){
            pair rem = pq.remove();
            int vtx = rem.vtx , wt = rem.wt;

            if(visited[vtx] == true){
                continue;
            }
            

            ans += wt;
            visited[vtx] = true;

            //adding neighours
            for(pair nbrs : graph.get(vtx)){
                if(visited[nbrs.vtx] == false)
                pq.add(nbrs);
            }

        }
        return ans;
    }
    
    public static class pair implements Comparable<pair>{
        int vtx , wt;

        pair(){

        }
        pair(int vtx , int wt){
            this.vtx = vtx;
            this.wt = wt;
        }

        public int compareTo(pair o){
            return this.wt - o.wt;
        }
    }
}