Add reorder-list solution in TS

Author: Jeehay28

reorder-list/Jeehay28.ts

@@ -0,0 +1,36 @@
+class ListNode {
+  val: number;
+  next: ListNode | null;
+  constructor(val?: number, next?: ListNode | null) {
+    this.val = val === undefined ? 0 : val;
+    this.next = next === undefined ? null : next;
+  }
+}
+
+/**
+ Do not return anything, modify head in-place instead.
+ */
+
+// TC: O(n)
+// SC: O(n)
+function reorderList(head: ListNode | null): void {
+  const nodes: ListNode[] = [];
+
+  while (head) {
+    nodes.push(head);
+    head = head.next;
+  }
+
+  let start = 0;
+  let end = nodes.length - 1;
+
+  while (start < end) {
+    nodes[start].next = nodes[end];
+    start++;
+    if (start === end) break;
+    nodes[end].next = nodes[start];
+    end--;
+  }
+
+  nodes[start].next = null;
+}