226 Invert Binary Tree

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/**  * Definition for a binary tree node.  * function TreeNode(val) {  *     this.val = val;  *     this.left = this.right = null;  * }  */ /**  * @param {TreeNode} root  * @return {TreeNode}  */ var invertTree = function(root) {     if(root == null) return null;     var tmpNode = root.left;     root.left = invertTree(root.right);     root.right = invertTree(tmpNode);     return root; };