Poison

138. Copy List with Random Pointer

发表于
HashMap
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class Solution {
    public Node copyRandomList(Node head) {
        if (head == null) {
            return null;
        }

        Map<Node, Node> oldToNewMap = new IdentityHashMap<>();
        Node node = head;
        while (node != null) {
            oldToNewMap.put(node, new Node(node.val));
            node = node.next;
        }

        for (Map.Entry<Node, Node> entry : oldToNewMap.entrySet()) {
            Node old = entry.getKey(), duplicate = entry.getValue();
            duplicate.next = oldToNewMap.get(old.next);
            duplicate.random = oldToNewMap.get(old.random);
        }

        return oldToNewMap.get(head);
    }
}
Linked List
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class Solution {
    public Node copyRandomList(Node head) {
        if (head == null) {
            return null;
        }

        Node curr = head;
        while (curr != null) {
            Node duplicate = new Node(curr.val);
            Node next = curr.next;
            curr.next = duplicate;
            duplicate.next = next;
            curr = next;
        }

        // nodeA -> duplicate nodeA -> nodeB -> duplicate nodeB -> ...

        curr = head;
        while (curr != null) {
            Node duplicate = curr.next;
            if (curr.random != null) {
                duplicate.random = curr.random.next;
            }
            curr = duplicate.next;
        }

        Node duplicateHead = head.next;
        curr = head;
        while (curr != null) {
            Node duplicate = curr.next;
            Node next = duplicate.next;
            curr.next = next;
            if (next != null) {
                duplicate.next = next.next;
            }
            curr = next;
        }

        return duplicateHead;
    }
}
Reference

138. Copy List with Random Pointer
剑指 Offer 35. 复杂链表的复制