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Invert Binary Tree

Problem statement​

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: []

Constraints:

  • The number of nodes in the tree is in the range [0, 100].
  • -100 <= Node.val <= 100

My solution​

/**
 * 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}
 */
var invertTree = function(root) {
    function invert(node) {
        if (!node) {
            return;
        }
        
        let left = node.left;
        let right = node.right;
        
        node.right = left;
        node.left = right;
        
        invert(node.right)
        invert(node.left)
    }
    
    invert(root)
    return root;
};