LeetCode - Remove Duplicates from Sorted List II
Problem description
Given 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 1:
1
2
Input: 1->2->3->3->4->4->5
Output: 1->2->5
Example 2:
1
2
Input: 1->1->1->2->3
Output: 2->3
Analysis
General idea is to use a if statement to check if contains duplicate, if so then skip all duplicates, if not then add the next item into the result;
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
public ListNode deleteDuplicates(ListNode head) {
if (head == null){
return head;
}
ListNode dummy = new ListNode(head.val - 1);
ListNode p = dummy;
dummy.next = head;
while (p.next != null){
int v = p.next.val;
if (p.next.next != null && p.next.next.val == v){
ListNode l = p.next;
while (l != null && l.val == v){
l = l.next;
}
p.next = l;
}
else{
p = p.next;
}
}
return dummy.next;
}
What to improve
- null checking for linked list questions.
