Create linked_list_reverse.js

Author: Aashi779

Linked List/linked_list_reverse.js

@@ -0,0 +1,43 @@
+//Problem statement-Given the head of a singly linked list, reverse the list, and return the reversed list.
+
+// Iteratively 
+* @param {ListNode} head
+ * @return {ListNode}
+ */
+var reverseList = function(head) {
+  // Handling the edge cases if head node is null or when single node is there 
+        if (head === null || head.next === null) {
+            return head;
+        }
+  // Using three pointer approach 
+        let prev = null;
+        let curr = head;
+        let fwd = null;
+        while (curr !== null) {
+          // Updatng the value of each of the pointers 
+            fwd = curr.next;
+            curr.next = prev;
+            prev = curr;
+            curr = fwd;
+        }
+  // Returning the head of the reversed linked list 
+        return prev;    
+};
+
+// Recursively 
+var reverseList = function(head) {
+  // Base case- If the head is null or single node is there
+  if (head === null || head.next === null) {
+    return head;
+  }
+
+  // Recursively reverse the remaining list starting from the next node 
+  const reversedList = reverseList(head.next);
+
+  // Reversing the links between the current and next node 
+  head.next.next = head;
+  head.next = null;
+
+  // Returning the head of the reversed linked list 
+  return reversedList; 
+};