138. Copy List with Random Pointer - jiejackyzhang/leetcode-note GitHub Wiki

A linked list is given such that each node contains an additional random pointer which could point to any node in the list or null.

Return a deep copy of the list.

解题思路为采用hash map来存储original node和copy node。 从而copy node的next和random都可以从original node得到。

/**
 * 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) {
        if(head == null) return null;
        Map<RandomListNode, RandomListNode> map = new HashMap<>();
        RandomListNode cur = head;
        while(cur != null) {
            map.put(cur, new RandomListNode(cur.label));
            cur = cur.next;
        }
        for(Map.Entry<RandomListNode, RandomListNode> entry : map.entrySet()) {
            RandomListNode node = entry.getValue();
            node.next = map.get(entry.getKey().next);
            node.random = map.get(entry.getKey().random);
        }
        return map.get(head);
    }
}