复制带随机指针的链表

import java.util.HashMap;
public class copylistwithRandom { //复制链表
  public static class Node {
    public int value;
    public Node next;
    public Node rand;

    public Node(int data) { this.value = data; }
  }
  //方法一:哈希表
  public static Node copyListWithRand1(Node head) {
    HashMap map = new HashMap();
    Node cur = head;

    while (cur != null) {
      map.put(cur, new Node(cur.value));
      cur = cur.next;
    }
    cur = head;
    while (cur != null) {
      map.get(cur).next = map.get(cur.next);
      map.get(cur).rand = map.get(cur.rand);
      cur = cur.next;
    }
    return map.get(head);
  }
  //方法二:节约空间的操作
  public static Node copyListWithRand2(Node head) {
    if (head == null)
      return null;
    Node cur = head;
    Node next = null;
    // copy node and link to every node
    while (cur != null) { // 节点复制
      next = cur.next;
      cur.next = new Node(cur.value);
      cur.next.next = next;
      cur = next;
    }
    cur = head;
    Node curCopy = null;
    // set copy node rand
    while (cur != null) {
      next = cur.next.next;
      curCopy = cur.next;
      curCopy.rand = cur.rand != null ? cur.rand : null;
      cur = next;
    }
    Node res = head.next;
    cur = head;
    while (cur != null) {
      next = cur.next.next;
      curCopy = cur.next;
      cur.next = next;
      curCopy.next = next != null ? next.next : null;
      cur = next;
    }
    return res;
  }
}