/**
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Definition for a binary tree node.
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function TreeNode(val, left, right) {
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this.val = (val===undefined ? 0 : val) -
this.left = (left===undefined ? null : left) -
this.right = (right===undefined ? null : right) -
} / /*
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@param {TreeNode} root
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@return {TreeNode} */ var invertTree = function(root) { if(root == null){ return root; }
let left = invertTree(root.left); let right = invertTree(root.right);
[root.left,root.right] = [root.right,root.left];
return root; };