LeetCode[138] Copy List with Random Pointer

LeetCode[138] Copy List with Random Pointer

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

Map

复杂度
O(N), O(N)

思路
和clone graph一样的思路。先copy顺序的，再copy那些random的pointer.

代码

public RandomListNode copyRandomList(RandomListNode node) {
    Map<RandomListNode, RandomListNode> map = new HashMap<>();
    RandomListNode dummy = new RandomListNode(0);
    RandomListNode p = head, q = head;
    // used to connect the new list;
    RandomListNode phead = dummy;
    while(p != null) {
        RandomListNode cp = new RandomListNode(p.label);
        map.put(p, cp);
        p = p.next;
        phead.next = cp;
        phead = phead.next;
    }
    while(q != null) {
        map.get(q).random = map.get(q.random);
        q = q.next;
    }
    return dummy.next;
}