java算法题解LeetCode35复杂链表的复制实例

class Solution {
	public Node copyRandomList(Node head) {
		// if head == null,则return null
		if (head == null) {
			return null;
		}
		// 第一次遍历， 1 -> `1` -> 2 -> `2` -> 3 - > `3` -> null
		Node cur = head;
		while (cur != null) {
			Node node = new Node(cur.val);
			Node temp = cur.next;
			cur.next = node;
			cur.next.next = temp;
			cur = cur.next.next;
		}
		// 第二次遍历，填充random节点
		cur = head;
		while (cur != null) {
			Node newNode = cur.next;
			newNode.random = cur.random != null ? cur.random.next : null;
			cur = cur.next.next;
		}
		// 第三次遍历，拆分
		Node headNew = head.next;
		for (Node node = head; node != null; node = node.next) {
			Node nodeNew = node.next;
			node.next = node.next.next;
			nodeNew.next = (nodeNew.next != null) ? nodeNew.next.next : null;
		}
		return headNew;
	}
	class Node {
		int val;
		Node next;
		Node random;
		public Node(int val) {
			this.val = val;
			this.next = null;
			this.random = null;
		}
	}
}