Add reorder-list solution

Author: Jeehay28

reorder-list/Jeehay28.js

@@ -0,0 +1,43 @@
+// ✅ Time Complexity: O(N)
+// ✅ Space Complexity: O(N) (due to the stack storage)
+
+/**
+ * Definition for singly-linked list.
+ * function ListNode(val, next) {
+ *     this.val = (val===undefined ? 0 : val)
+ *     this.next = (next===undefined ? null : next)
+ * }
+ */
+
+/**
+ * @param {ListNode} head
+ * @return {void} Do not return anything, modify head in-place instead.
+ */
+var reorderList = function (head) {
+  let stack = [];
+  let node = head;
+
+  while (node) {
+    stack.push(node);
+    node = node.next;
+  }
+
+  let dummy = new ListNode(-1);
+  node = dummy;
+
+  const len = stack.length;
+
+  for (let i = 0; i < len; i++) {
+    if (i % 2 === 1) {
+      node.next = stack.pop();
+    } else {
+      node.next = head;
+      head = head.next;
+    }
+    node = node.next;
+  }
+
+  node.next = null;
+  return dummy.next;
+};
+