138. Copy List with Random Pointer

答案

/**
 * Definition for singly-linked list with a random pointer.
 * class RandomListNode {
 *     int label;
 *     RandomListNode next, random;
 *     RandomListNode(int x) { this.label = x; }
 * };
 */
public class Solution {
    public RandomListNode copyRandomList(RandomListNode head) {
        Map<RandomListNode, RandomListNode> map = new HashMap<RandomListNode, RandomListNode>();

        RandomListNode p = head;
        while (p != null) {
            map.put(p, new RandomListNode(p.label));
            p = p.next;
        }

        p = head;
        while (p != null) {
            RandomListNode node = map.get(p);
            node.next = map.get(p.next);
            node.random = map.get(p.random);
            p = p.next;
        }

        return map.get(head);
    }
}

图文详解

参考

Java O(n) solution