class Solution {
     public TreeNode invertTree(TreeNode node) {
        if(node==null)return node;
        TreeNode temp = node.left;
        node.left = node.right;
        node.right = temp;
        node.left = invertTree(node.left);
        node.right = invertTree(node.right);
        return node;
    }
}
class Solution {
     public TreeNode invertTree(TreeNode node) {
        if(node==null)return node;
        TreeNode temp = node.left;
        node.left = node.right;
        node.right = temp;
        invertTree(node.left);
        invertTree(node.right);
        return node;
    }
}