Create 234-palindrome-linked-list

Author: BassemHalim

c/0234-palindrome-linked-list.c

@@ -0,0 +1,36 @@
+/**
+ * Definition for singly-linked list.
+ * struct ListNode {
+ *     int val;
+ *     struct ListNode *next;
+ * };
+ */
+bool isPalindrome(struct ListNode* head){
+
+    // find middle of linked list
+    struct ListNode *slow = head, *fast = head;
+    while (fast && fast->next){
+        slow = slow->next;
+        fast = fast->next->next;
+    }
+    // reverse second half
+    struct ListNode* prev = NULL;
+    while (slow){
+        struct ListNode* nxt = slow->next;
+        slow->next = prev;
+        prev = slow;
+        slow = nxt;
+    }
+
+    // compare left and right
+    struct ListNode *left=head, *right=prev;
+    while (right){
+        if (left->val != right->val){
+            return false;
+        }
+        left = left->next;
+        right = right->next;
+    }
+    return true;
+    
+}