LeetCode-82. Remove Duplicates From Sorted List II

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问题描述

Given the head of a sorted linked list, delete all nodes that have duplicate numbers, leaving only distinct numbers from the original list. Return the linked list sorted as well.

Example :

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Input: head = [1,2,3,3,4,4,5]
Output: [1,2,5]

Constraints:

  • The number of nodes in the list is in the range [0, 300].
  • -100 <= Node.val <= 100
  • The list is guaranteed to be sorted in ascending order.

解答

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/*
 * @Description: 82. Remove Duplicates from Sorted List II
 * @Author: libk
 * @Github: https://github.com/libk
 */
/**
 * Definition for singly-linked list.
 * function ListNode(val, next) {
 *     this.val = (val===undefined ? 0 : val)
 *     this.next = (next===undefined ? null : next)
 * }
 */
/**
 * @param {ListNode} head
 * @return {ListNode}
 */
const deleteDuplicates = function(head) {
  let dummy = new ListNode()
  dummy.next = head
  let pre = dummy
  let cur = head

  while (cur !== null) {
    while (cur.next !== null && cur.val === cur.next.val) {
      cur = cur.next
    }
    // 判断是否有重复项
    if (pre.next === cur) {
      pre = cur
    } else {
      pre.next = cur.next
    }
    cur = cur.next
  }
  return dummy.next
}