(UVA) Dark Roads - Solution 1

I used Kruskal's algorithm to solve this problem.


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

class Main  {
    public static int[] nodeParent;
    public static int[] depth;
   
    public static int root(int n) {
        int currN = n;
        while (nodeParent[currN] != currN) {
            currN = nodeParent[currN];
        }
       
        return currN;
    }
   
    public static boolean union(int n1, int n2) {
        int rootN1 = root(n1);
        int rootN2 = root(n2);
       
        if (rootN1 != rootN2) {
            if (depth[rootN1] >= depth[rootN2]) {
                nodeParent[rootN2] = nodeParent[rootN1];               
                if (depth[rootN1] == depth[rootN2]) {
                    depth[rootN1]++;
                }
            }
            else {
                nodeParent[rootN1] = nodeParent[rootN2];
            }
           
            return true;
        }
       
        return false;
    }
   
    public static void process() throws NumberFormatException, IOException {  
        Scanner sc = new Scanner(System.in);
       
        int numJunctions = sc.nextInt();
        int numRoads = sc.nextInt();
        while (numJunctions != 0 || numRoads != 0) {
            ArrayList<Edge> edges = new ArrayList<Edge>();
            for (int i = 0; i < numRoads; i++) {
                int n1 = sc.nextInt();
                int n2 = sc.nextInt();
                int cost = sc.nextInt();
                edges.add(new Edge(n1, n2, cost));
            }
           
            Collections.sort(edges);
           
            nodeParent = new int[numJunctions];
            depth = new int[numJunctions];
            for (int i = 0; i < numJunctions; i++) {
                nodeParent[i] = i;
                depth[i] = 0;
            }
           
            int save = 0;
            for (int i = 0; i < edges.size(); i++) {
                if (!union(edges.get(i).n1, edges.get(i).n2)) {
                    save += edges.get(i).cost;
                }           
            }
           
            System.out.println(save);
           
            numJunctions = sc.nextInt();
            numRoads = sc.nextInt();
        }
                                               
        return;
    }
  
    public static void main(String[] args) throws NumberFormatException, IOException {
        Main m = new Main();
        m.process();

        System.exit(0);
    }
}

class Edge implements Comparable<Edge> {
    int n1;
    int n2;
    int cost;
   
    public Edge(int n1, int n2, int cost) {
        this.n1 = n1;
        this.n2 = n2;
        this.cost = cost;
    }
   
    public int compareTo(Edge e) {
        return this.cost-e.cost;
    }
}