Add same-tree solution in TS

Author: Jeehay28

same-tree/Jeehay28.ts

@@ -0,0 +1,41 @@
+class TreeNode {
+  val: number;
+  left: TreeNode | null;
+  right: TreeNode | null;
+  constructor(val?: number, left?: TreeNode | null, right?: TreeNode | null) {
+    this.val = val === undefined ? 0 : val;
+    this.left = left === undefined ? null : left;
+    this.right = right === undefined ? null : right;
+  }
+}
+
+// TC: O(n)
+// SC: O(n)
+function isSameTree(p: TreeNode | null, q: TreeNode | null): boolean {
+  if (!p && !q) return true;
+  if (!p || !q) return false;
+
+  if (p.val !== q.val) return false;
+
+  return isSameTree(p.left, q.left) && isSameTree(p.right, q.right);
+}
+
+
+// TC: O(n)
+// SC: O(n)
+// function isSameTree(p: TreeNode | null, q: TreeNode | null): boolean {
+//   const stack: (TreeNode | null)[][] = [[p, q]];
+
+//   while (stack.length > 0) {
+//     const [node1, node2] = stack.pop();
+
+//     if (!node1 && !node2) continue;
+//     if (!node1 || !node2) return false;
+//     if (node1.val !== node2.val) return false;
+
+//     stack.push([node1.left, node2.left]);
+//     stack.push([node1.right, node2.right]);
+//   }
+
+//   return true;
+// }