QuickFind.java

import edu.princeton.cs.algs4.StdIn;
import edu.princeton.cs.algs4.StdOut;

public class QuickFind {
    
    private int[] id;
    
    public QuickFind(int N) {
        id = new int[N];
        for(int i = 0; i < N; i++) {
            id[i] = i;
        }
    }
    
    public boolean connected(int p, int q) {
        return id[p] == id[q];
    }
    
    public void union(int p, int q) {
        int pid = id[p];
        int qid = id[q];
        for(int i = 0; i < id.length; i++) {
            if(id[i] == pid) {
                id[i] = id[q];
            }
        }
    }
    
    public static void main(String args[]) {
        int noOfElements = StdIn.readInt();
        QuickFind qf = new QuickFind(noOfElements);
        while(!StdIn.isEmpty()) {
            int p = StdIn.readInt();
            int q = StdIn.readInt();
            if(!qf.connected(p, q)) {
                qf.union(p, q);
                StdOut.println(p + " " + q);
            }
        }
    } 
}