Time: 474 ms, Memory: 52.1 MB - LeetHub

Author: froghramar

palindrome-linked-list/palindrome-linked-list.cs

@@ -0,0 +1,70 @@
+/**
+ * Definition for singly-linked list.
+ * public class ListNode {
+ *     public int val;
+ *     public ListNode next;
+ *     public ListNode(int val=0, ListNode next=null) {
+ *         this.val = val;
+ *         this.next = next;
+ *     }
+ * }
+ */
+public class Solution {
+    public bool IsPalindrome(ListNode head) {
+        if (head == null)
+        {
+            return true;
+        }
+
+        var mid = FindMid(head);
+        var last = ReverseAfter(mid);
+        mid.next = null;
+
+        ListNode headIterator = head, lastIterator = last;
+        while (lastIterator != null)
+        {
+            if (lastIterator.val != headIterator.val)
+            {
+                return false;
+            }
+
+            lastIterator = lastIterator.next;
+            headIterator = headIterator.next;
+        }
+
+        return true;
+    }
+
+    ListNode ReverseAfter(ListNode node)
+    {
+        ListNode current = node, next = current.next;
+        while (next != null)
+        {
+            var secondNext = next.next;
+            next.next = current;
+            current = next;
+            next = secondNext;
+        }
+
+        return current;
+    }
+
+    ListNode FindMid(ListNode head)
+    {
+        ListNode mid = head, current = head;
+        var even = true;
+
+        while (current.next != null)
+        {
+            if (even)
+            {
+                mid = mid.next;
+            }
+
+            current = current.next;
+            even = !even;
+        }
+
+        return mid;
+    }
+}