invertBinaryTree.js

////////////////////////////////////////////////Invert Binary Tree/////////////////////////////////////////////
// Given the root of a binary tree, invert the tree, and return its root.
// Example 1:
// Input: root = [4,2,7,1,3,6,9]
// Output: [4,7,2,9,6,3,1]
// Example 2:
// Input: root = [2,1,3]
// Output: [2,3,1]
// Example 3:
// Input: root = []
// Output: []
/**
 * Definition for a binary tree node.
 * function TreeNode(val, left, right) {
 *     this.val = (val===undefined ? 0 : val)
 *     this.left = (left===undefined ? null : left)
 *     this.right = (right===undefined ? null : right)
 * }
 */
/**
 * @param {TreeNode} root
 * @return {TreeNode}
 */
 const invertTree = function(root) {
    if(root === null) return root;
    let left = invertTree(root.left);
    let right = invertTree(root.right);

    root.left = right;
    root.right = left;

    return root;
};

// console.log(invertTree([4,2,7,1,3,6,9]));
// console.log(invertTree([2,1,3]));
// console.log(invertTree([]));