ALGORITHM1.5(continued) Union-find inplementation (weighted quick-union)

import edu.princeton.cs.algs4.*;

public class WeightedQuickUnionUF
{
    private int[] id;
    private int[] sz;
    private int count;
    
    public WeightedQuickUnionUF(int N)
    {
        count = N;
        id = new int[N];
        for(int i = 0; i < N; i++)
            id[i] = i;
        sz = new int[N];
        for(int i = 0; i < N; i++)
            sz[i] = 1;
    }
    
    public int count()
    {
        return count;
    }
    
    public boolean connected(int p, int q)
    {
        return find(p) == find(q);
    }
    
    public int find(int p)
    {
        while(p != id[p])
            p = id[p];
        return p;
    }
    
    public void union(int p, int q)
    {
        int i = find(p);
        int j = find(q);
        if(i == j)
            return;
        if(sz[i] < sz[j])
        {
            id[i] = j;
            sz[j] += sz[i];
        }
        else
        {
            id[j] = i;
            sz[i] += sz[j];
        }
        count--;
    }
    
    public static void main(String[] args)
    {
        int N = StdIn.readInt();
        UF uf = new UF(N);
        while(!StdIn.isEmpty())
        {
            int p = StdIn.readInt();
            int q = StdIn.readInt();
            if(uf.connected(p,q))
                continue;
            uf.union(p,q);
            StdOut.println(p + " " + q);
        }
        StdOut.println(uf.count() + " components");
    }
}