How LeetCode removes repeating elements from a sorted list
This article will explain in detail how to delete the repeated elements in the sorted list by LeetCode. The editor thinks it is very practical, so I share it with you as a reference. I hope you can get something after reading this article.
1. Brief introduction of the problem.
Given a sorted linked list, delete all nodes that contain duplicate numbers, leaving only those numbers that are not repeated in the original linked list.
2, example
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
3, the train of thought of solving the problem
Use the Sentinel node to solve the set LinkedHashMap collection with key values.
4, problem solving procedure
Import java.util.*;import java.util.stream.Collectors
Public class DeleteDuplicatesTest3 {public static void main (String [] args) {ListNode L1 = new ListNode (1); ListNode L2 = new ListNode (2); ListNode L3 = new ListNode (3); ListNode L4 = new ListNode (3); ListNode L5 = new ListNode (4); ListNode L6 = new ListNode (4); ListNode L7 = new ListNode (5); l1.next = L2; l2.next = L3 L3.next = L4; l4.next = 15; l5.next = L6; l6.next = L7; ListNode listNode = deleteDuplicates (L1); System.out.println ("listNode =" + listNode);}
Public static ListNode deleteDuplicates (ListNode head) {if (head = = null) {return null;} if (head.next = = null) {return head;} HashMap hashMap = new LinkedHashMap (); ListNode dummyNode = head; while (dummyNode! = null) {hashMap.put (dummyNode.val, hashMap.getOrDefault (dummyNode.val, 0) + 1) DummyNode = dummyNode.next;} List list = hashMap.entrySet (). Stream (). Filter (Objects::nonNull) .filter (x-> x.getValue () = = 1) .map (Map.Entry::getKey) .filter (Collectors.toList ()); ListNode newHead = new ListNode (- 1); int size = list.size (); ListNode tempNode = newHead; for (int I = 0) I < size; iTunes +) {tempNode.next = new ListNode (list.get (I)); tempNode = tempNode.next;} return newHead.next;}
}
5. Picture version of the problem solving program.
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