Union Find Data Structure

UnionFind.java

public class UnionFind {

    private int id[];

    private int count;

    public UnionFind(int N) {
        count = N;
        id = new int[N];
        for(int i = 0; i < N; i++) {
            id[i] = i;
        }
    }

    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) {
            id[i] = j;
            count--;
        }
    }

}