LeetCode82----删除排序链表中的重复元素 II

Posted 2020-11-17 book808

给定一个排序链表，删除所有含有重复数字的节点，只保留原始链表中 没有重复出现 的数字。

示例 1:

输入: 1->2->3->3->4->4->5
输出: 1->2->5

示例 2:

输入: 1->1->1->2->3
输出: 2->3

代码如下：

public class MyLeetCode82 {
	public static class ListNode {
		int val;
		ListNode next;

		ListNode(int x) {
			val = x;
		}
	}

	public static ListNode deleteDuplicates(ListNode head) {
		if (head == null || head.next == null) {
			return head;
		}
		ListNode fakeNode = new ListNode(-1);
		ListNode root = fakeNode;
		ListNode prev = head;
		ListNode cur = head;
		while (cur != null && cur.next != null) {
			while (cur.next != null && cur.next.val == prev.val) {
				cur = cur.next;
			}
			if (cur == prev) {
				// 指针没动过,代表当前第一个就是不重复的
				root.next = prev;
				root = root.next;
			}
			prev = cur.next;
			cur = cur.next;
		}
		if (prev == cur && prev != null) {
			root.next = cur;
			root = root.next;
		}
		root.next = null;
		return fakeNode.next;
	}
}