struct Tree()
{
int val;
Tree *left, *right;
Tree(int a): val(a), left(NULL), right(NULL){}
}
bool mirrorTree(Tree *root){
if(root == NULL || (root->left== NULL && root->right == NULL)) return NULL ;
Tree *tp = root->left;
root->left = root->right;
root->right = tp;
if(root->left)
mirrorTree(root->left);
if(root->right)
mirrorTree(root->right);
}