Java使用HashMap实现并查集

public static class Node {
 // Node可以是任意的类型 int， String等等
 }

 public static class UnionFind {
 public HashMap<Node, Node> fatherMap; // 用来存放每个节点的头节点
 public HashMap<Node, Integer> sizeMap; // 用来保存每个集合的大小

 public UnionFind() {
  fatherMap = new HashMap<Node, Node>();
  sizeMap = new HashMap<Node, Integer>();
 }

 public void makeSet(List<Node> nodes) {
  fatherMap.clear();
  sizeMap.clear();
  for (Node node : nodes) {
  fatherMap.put(node, node); // 每个节点单独成为一个集合，头节点指向自己
  sizeMap.put(node, 1); // 初始化时每个集合的大小为1
  }
 }

 private Node findHead(Node node) {
  Node father = fatherMap.get(node);
  while (father != node) {
  father = findHead(father); // 递归向上找
  }
  fatherMap.put(node, father); // 每次递归时都把每个节点的父节点直接指向头节点
  return father;
 }

 public boolean isSameSet(Node aNode, Node bNode) {
  return findHead(aNode) == findHead(bNode);
 }

 public void union(Node aNode, Node bNode) {
  if (aNode == null || bNode == null) {
  return;
  }
  Node aHead = findHead(aNode);
  Node bHead = findHead(bNode);
  if (aHead != bHead) {
  int aSize = sizeMap.get(aHead);
  int bSize = sizeMap.get(bHead);
  if (aSize <= bSize) {
   fatherMap.put(aHead, bHead);
   sizeMap.put(bHead, aSize + bSize);
  } else {
   fatherMap.put(bHead, aHead);
   sizeMap.put(aHead, aSize + bSize);
  }
  }
 }
 }