From 566136b57d487df7ad20f086450b2f40ec0511cc Mon Sep 17 00:00:00 2001
From: rsimpson2 <rsimpson2@me.com>
Date: Sat, 24 Jan 2026 08:07:52 -0500
Subject: [PATCH] Blind 75: Flip Binary Tree

---
 README.md                                     |  8 +---
 greatfrontend/blind-75/README.md              |  1 +
 .../blind-75/trees/flip-binary-tree/README.md | 42 +++++++++++++++++++
 .../flip-binary-tree/flip-binary-tree.ts      | 23 ++++++++++
 4 files changed, 67 insertions(+), 7 deletions(-)
 create mode 100644 greatfrontend/blind-75/trees/flip-binary-tree/README.md
 create mode 100644 greatfrontend/blind-75/trees/flip-binary-tree/flip-binary-tree.ts

diff --git a/README.md b/README.md
index 8c1a75f..9b7ecdd 100644
--- a/README.md
+++ b/README.md
@@ -7,7 +7,7 @@ A comprehensive collection of coding challenges from multiple platforms for lear
 | Platform                        | Focus Area                   | Problems Solved |
 | ------------------------------- | ---------------------------- | --------------- |
 | [LeetCode](#leetcode)           | Data Structures & Algorithms | 171             |
-| [GreatFrontEnd](#greatfrontend) | Frontend Engineering         | 13              |
+| [GreatFrontEnd](#greatfrontend) | Frontend Engineering         | 14              |
 
 ## Platforms
 
@@ -23,12 +23,6 @@ Various places where I enjoy practicing solving coding challenges:
 
 **Focus**: Data structures, algorithms, and problem-solving patterns
 
-**Progress**:
-
-- Easy: 80 problems
-- Medium: 77 problems
-- Hard: 14 problems
-
 **Quick Links**:
 
 - [Browse LeetCode Solutions →](./leetcode/)
diff --git a/greatfrontend/blind-75/README.md b/greatfrontend/blind-75/README.md
index d1d62e0..013572c 100644
--- a/greatfrontend/blind-75/README.md
+++ b/greatfrontend/blind-75/README.md
@@ -28,6 +28,7 @@ No problems completed yet
 
 - [Binary Search Tree Kth Smallest Element](./trees/bst-kth-smallest/) - Medium
 - [Binary Tree Level Order Traversal](./trees/level-order-traversal/) - Medium
+- [Flip Binary Tree](./trees/flip-binary-tree/) - Easy
 
 ### Dynamic Programming
 
diff --git a/greatfrontend/blind-75/trees/flip-binary-tree/README.md b/greatfrontend/blind-75/trees/flip-binary-tree/README.md
new file mode 100644
index 0000000..d81636d
--- /dev/null
+++ b/greatfrontend/blind-75/trees/flip-binary-tree/README.md
@@ -0,0 +1,42 @@
+# Flip Binary Tree ![Shield](https://img.shields.io/badge/Level-Easy-green) ![Shield](https://img.shields.io/badge/Category-Trees-blue)
+
+Link to problem: [https://www.greatfrontend.com/interviews/study/blind75/questions/algo/binary-tree-flip](https://www.greatfrontend.com/interviews/study/blind75/questions/algo/binary-tree-flip)
+
+Given the `root` node of a binary tree, flip the tree by swapping each node's left and right children, then return the root of the flipped tree.
+
+The binary tree is represented by a collection of `TreeNodes`, where each node has optional `left` and `right` child nodes, which are also `TreeNode`s.
+
+A TreeNode has the following interface:
+
+```typescript
+interface TreeNode {
+  val: number;
+  left: TreeNode | null;
+  right: TreeNode | null;
+}
+```
+
+## Input
+
+- `root: TreeNode`: Root node of the tree. Examples display a level-order traversal of the tree
+
+## Examples
+
+```plaintext
+Input: root = [2,1,3]
+Output: [2,3,1]
+Explanation: The left and right children are swapped.
+
+Input: root = [43,null,-55]
+Output: [43,-55]
+Explanation: The right child becomes the left child after inversion.
+
+Input: root = [12,8,18,6,null,null,20]
+Output: [12,18,8,20,null,null,6]
+Explanation: The tree is inverted, with left and right children of each node being swapped.
+```
+
+## Constraints
+
+- 1 <= Number of nodes <= 100
+- -100 <= `TreeNode.val` <= 100
diff --git a/greatfrontend/blind-75/trees/flip-binary-tree/flip-binary-tree.ts b/greatfrontend/blind-75/trees/flip-binary-tree/flip-binary-tree.ts
new file mode 100644
index 0000000..4df8510
--- /dev/null
+++ b/greatfrontend/blind-75/trees/flip-binary-tree/flip-binary-tree.ts
@@ -0,0 +1,23 @@
+export interface TreeNode {
+  val: number;
+  left: TreeNode | null;
+  right: TreeNode | null;
+}
+
+/**
+ * @time O(n) where n is each node in the tree
+ * @space O(h) where h is the height of the tree
+ */
+export function flipBinaryTree(root: TreeNode | null): TreeNode | null {
+  if (root === null) {
+    return null;
+  }
+
+  const rightNode = flipBinaryTree(root.right);
+  const leftNode = flipBinaryTree(root.left);
+
+  root.left = rightNode;
+  root.right = leftNode;
+
+  return root;
+}