0082. Remove Duplicates from Sorted List II (M)

Remove Duplicates from Sorted List II (M)

题目

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

Example 1:

Input: 1->2->3->3->4->4->5
Output: 1->2->5

Example 2:

Input: 1->1->1->2->3
Output: 2->3

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题意

将有序链表中所有值重复的结点删除，只保留值不重复的结点。

思路

遍历链表，找到所有值不重复的结点，将其单独取出来依次加入到新链表中。

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代码实现

Java

class Solution {
    public ListNode deleteDuplicates(ListNode head) {
        ListNode ans = null, last = null;
        
        while (head != null) {
            ListNode temp = head.next;
            int count = 0;
            
            // 判断head的值是否重复，并找到下一个值不同的结点
            while (temp != null && temp.val == head.val) {
                temp = temp.next;
                count++;
            }
            
            if (count == 0) {
                head.next = null;		// 将该结点单独取出，断开与之后结点的联系
                if (ans == null) {
                    ans = head;
                    last = head;
                } else {
                    last.next = head;
                    last = last.next;
                }
            }
            
            head = temp;
        }

        return ans;
    }
}

JavaScript

/**
 * @param {ListNode} head
 * @return {ListNode}
 */
var deleteDuplicates = function (head) {
  const dummy = new ListNode()
  let p = dummy
  while (head) {
    if (head.next && head.next.val === head.val) {
      const val = head.val
      while (head && head.val === val) {
        head = head.next
      }
    } else {
      p.next = head
      p = head
      head = head.next
      p.next = null
    }
  }
  return dummy.next
}