Modified reorder list solution

Author: nhistory

reorder-list/nhistory.js

@@ -1,3 +1,4 @@
+// First option : change node value
 var reorderList = function (head) {
   if (!head) return;
   // Create new arr to return result and current head
@@ -24,3 +25,44 @@ var reorderList = function (head) {
 
 // TC: O(n)
 // SC: O(n)
+
+// Second option : move node without changing values
+var reorderList = function (head) {
+  // Edge case
+  if (!head) return;
+
+  // Find mid node from linked list
+  let slow = head,
+    fast = head;
+  while (fast && fast.next) {
+    slow = slow.next;
+    fast = fast.next.next;
+  }
+
+  // Reverse second half list
+  let prev = null,
+    curr = slow,
+    temp;
+  while (curr) {
+    temp = curr.next;
+    curr.next = prev;
+    prev = curr;
+    curr = temp;
+  }
+
+  // Modify linked list as followed instruction
+  let first = head,
+    second = prev;
+  while (second.next) {
+    temp = first.next;
+    first.next = second;
+    first = temp;
+
+    temp = second.next;
+    second.next = first;
+    second = temp;
+  }
+};
+
+// TC: O(n)
+// SC: O(1)