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[leetcode] problem 138 – copy list with random pointer

admin 11月 13, 2020 0

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.

Example

Input:
{“$id”:”1”,”next”:{“$id”:”2”,”next”:null,”random”:{“$ref”:”2”},”val”:2},”random”:{“$ref”:”2”},”val”:1}

Explanation:
Node 1’s value is 1, both of its next and random pointer points to Node 2.
Node 2’s value is 2, its next pointer points to null and its random pointer points to itself.

Code

public class  {
    int label;
    RandomListNode next, random;
    RandomListNode(int x) { this.label = x; }
 }


public RandomListNode copyRandomList(RandomListNode head) {
    RandomListNode current = head;
    RandomListNode copyHead = null, copyCurrent = null;

    while (current != null) {
        RandomListNode copy = new RandomListNode(current.label);
        copy.next = current.next;
        current.next = copy;
        current = copy.next;
    }

    current = head;

    while (current != null) {
        if (current.random != null)
            current.next.random = current.random.next;

        current = current.next.next;
    }

    current = head;

    if (current != null) {
        copyHead = copyCurrent = current.next;
        current.next = current.next.next;
        current = copyCurrent.next;
    }

    while (current != null) {
        copyCurrent.next = current.next;
        current.next = current.next.next;
        copyCurrent = copyCurrent.next;
        current = current.next;
    }

    return copyHead;
}