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删除链表中重复的节点

删除链表中重复的节点

题目描述

在一个排序的链表中,存在重复的结点,请删除该链表中重复的结点,重复的结点不保留,返回链表头指针。 例如,链表1->2->3->3->4->4->5 处理后为 1->2->5

解法

解法一:递归

/**
 * @author bingo
 * @since 2018/11/21
 */

/*
 public class ListNode {
    int val;
    ListNode next = null;

    ListNode(int val) {
        this.val = val;
    }
}
*/
public class Solution {
    /**
     * 删除链表重复的节点
     * @param pHead 链表头节点
     * @return 删除节点后的链表
     */
    public ListNode deleteDuplication(ListNode pHead) {
        if (pHead == null || pHead.next == null) {
            return pHead;
        }

        if (pHead.val == pHead.next.val) {
            if (pHead.next.next == null) {
                return null;
            }
            if (pHead.next.next.val == pHead.val) {
                return deleteDuplication(pHead.next);
            }
            return deleteDuplication(pHead.next.next);
        }
        pHead.next = deleteDuplication(pHead.next);
        return pHead;
    }
}

解法二

/*
 public class ListNode {
    int val;
    ListNode next = null;

    ListNode(int val) {
        this.val = val;
    }
}
*/
public class Solution {
    public ListNode deleteDuplication(ListNode pHead) {
        if (pHead == null || pHead.next == null) {
            return pHead;
        }

        ListNode pre = null;
        ListNode cur = pHead;
        while (cur != null) {
            if (cur.next != null && cur.next.val == cur.val) {
                int val = cur.val;
                while (cur.next != null && cur.next.val == val) {
                    cur = cur.next;
                }
                if (pre == null) {
                    pHead = cur.next;
                } else {
                    pre.next = cur.next;
                }
            } else {
                pre = cur;
            }
            cur = cur.next;
        }
        return pHead;
    }
}

测试用例

  1. 功能测试(重复的节点位于链表的头部/中间/尾部;链表中没有重复的节点);
  2. 特殊输入测试(指向链表头节点的为空指针;链表中所有节点都是重复的)。


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