Invert Binary Tree

The Problem Given the root of a binary tree, invert the tree, and return its root. Examples Input: root = [4,2,7,1,3,6,9] Output: [4,7,2,9,6,3,1] Input: root = [2,1,3] Output: [2,3,1] Input: root = [] Output: [] Constraints The number of nodes in the tree is in the range [0, 100]. -100 <= Node.val <= 100 Depth First Search Solution func invertTree(_ root: TreeNode?) -> TreeNode? { if root == nil { return nil } let tmp = root?.left root?.left = root?.right root?.right = tmp invertTree(root?.left) invertTree(root?.right) return root } Explanation When working with trees, we often consider two general ways to solve these problems: depth-first search (DFS) and breadth-first search (BFS). In this case, we use the DFS algorithm, where we swap the left subtree with the right subtree and recursively call invertTree on the left and right nodes. ...