加权路径压缩并查集实现

package algs4;

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

import java.io.FileInputStream;
import java.io.InputStream;

/**
* 并查集
* Created by blank on 2015-10-15 下午8:56.
*/
public class UF {

public static void main(String[] args) throws Exception {
InputStream input = new FileInputStream(Constants.PATH + "largeUF.txt");
System.setIn(input);
int N = StdIn.readInt();
UF uf = new UF(N);
while (N-- > 0) {
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.getCount() + " components");

}

private int[] parent;
private byte[] rank;
private int count;

public UF(int n) {
count = n;
parent = new int
;
rank = new byte
;
for (int i = 0; i < n; i++) {
parent[i] = i;
rank[i] = 0;
}
}

public int getCount() {
return count;
}

public boolean connected(int p, int q) {
return find(p) == find(q);
}

private int find(int p) {
while (p != parent[p]) {
parent[p] = parent[parent[p]];
p = parent[p];
}
return p;
}

public void union(int p, int q) {
int rootP = find(p);
int rootQ = find(q);
if (rootP == rootQ) {
return;
}
if (rank[rootP] < rank[rootQ]) {
parent[rootP] = rootQ;
} else if (rank[rootP] > rank[rootQ]) {
parent[rootQ] = rootP;
} else {
parent[rootP] = rootQ;
rank[rootQ]++;
}
count--;
}

}