Feat: 226. Invert Binary Tree

Author: HC-kang

invert-binary-tree/HC-kang.ts

@@ -0,0 +1,48 @@
+// 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;
+//   }
+// }
+
+/**
+ * https://leetcode.com/problems/invert-binary-tree
+ * T.C. O(n)
+ * S.C. O(n)
+ */
+function invertTree(root: TreeNode | null): TreeNode | null {
+  if (root === null) {
+    return null;
+  }
+
+  [root.left, root.right] = [root.right, root.left];
+  invertTree(root.left);
+  invertTree(root.right);
+
+  return root;
+}
+
+/**
+ * T.C. O(n)
+ * S.C. O(n)
+ */
+function invertTree(root: TreeNode | null): TreeNode | null {
+  const stack: Array<TreeNode | null> = [root];
+
+  while (stack.length > 0) {
+    const node = stack.pop()!;
+
+    if (node === null) {
+      continue;
+    }
+
+    [node.left, node.right] = [node.right, node.left];
+    stack.push(node.left, node.right);
+  }
+
+  return root;
+}