leetcode

commit 86cb2f9baa158a1f511a2697e38ef27afe49981f
parent 92277f1ab4946d5f977afe2d85fa0197eab06a3a
Author: AndrewLockVI <andrewlaack1@gmail.com>
Date:   Fri, 21 Apr 2023 15:25:37 -0500

Reverse linked list in dart

Diffstat:
A
reverse-linked-list/reverse-list.dart
 | 
40
++++++++++++++++++++++++++++++++++++++++

1 file changed, 40 insertions(+), 0 deletions(-)
diff --git a/reverse-linked-list/reverse-list.dart b/reverse-linked-list/reverse-list.dart
@@ -0,0 +1,40 @@
+//This algorithm reverses the order of a linked list.
+//To do this it puts all of the values into a list and then
+//iterates through the list in reverse order placing each iterated value
+//into a new linked list. From there it returns that head of the new list.
+//The time complexity of this is O(n) where n is the length of the list.
+//Runtime: 239ms Beats: 93.94%
+//Memory: 142.5MB Beats: 77.78%
+
+/**
+ * Definition for singly-linked list.
+ * class ListNode {
+ *   int val;
+ *   ListNode? next;
+ *   ListNode([this.val = 0, this.next]);
+ * }
+ */
+class Solution {
+  ListNode? reverseList(ListNode? head) {
+    if(head == null){
+      return null;
+    }
+
+      List<ListNode?> nodes = [];
+      while(head != null){
+        nodes.add(head);
+        head = head.next;
+      }
+      ListNode? ln1 = new ListNode();
+      ln1.val = nodes[nodes.length - 1]?.val ?? 0;
+      head = ln1;
+      ListNode? ln2;
+      for(int i = nodes.length - 2 ; i >= 0 ; --i){
+        ln2 = new ListNode();
+        ln2.val = nodes[i]?.val ?? 0;
+        ln1?.next = ln2;
+        ln1 = ln2;
+      }
+      return head;
+  }
+}