不相交集

public class DisjoinSet 
{

    public static void main(String[] args)
    {
        DisjoinSet disjoin = new DisjoinSet(8);

        disjoin.union(4, 3);
        disjoin.union(5, 4);
        disjoin.union(6, 5);
        disjoin.union(7, 6);
        disjoin.union(8, 7);
        
        int c = disjoin.find(3);
        disjoin.display();
    }
    
    
    private int n;
    
    private int[] parents;
    
    private int[] rank;
    
    
    public DisjoinSet(int n)
    {
        this.n = n;
        init();
    }

    private void init()
    {
        parents = new int[n + 1];
        rank = new int[n + 1];
        
        for (int i = 1; i <= n; i++) {
            parents[i] = i;
            rank[i] = i;
        }
    }
    
    public int find(int x)
    {
        int parent = x;
        while (parent != parents[parent]) {
            parent = parents[parent];
        }
        
        disjoin(x, parent);
        return parent;
    }
    
    private void disjoin(int x, int parent)
    {
        int temp;
        while (x != parent) {
            temp = parents[x];
            parents[x] = parent;
            x = temp;
        }
    }
    
    public void union(int a, int b)
    {
        int compare = compare(rank[a], rank[b]); 
        if (compare == 1) {
            parents[b] = a;
        }
        else {
            parents[a] = b;
        }
    }
    
    private int compare(int a, int b)
    {
        return a > b ? 1 : a < b ? -1 : 0;
    }
    
    public void display()
    {
        for (int i : rank) {
            System.out.print(" " + i + " ");
        }
        
        System.out.println();
        
        for (int i : parents) {
            System.out.print(" " + i + " ");
        }
    }
}