* Definition for a binary tree node.
* TreeNode(int x) : val(x), left(NULL), right(NULL) {}
TreeNode* pruneTree(TreeNode* root) {
if(!root->left && !root->right) return (!isRoot && root->val == 0) ? nullptr: root;
// cout<<root->val<<endl;
if(root->left ) root->left = pruneTree(root->left);
if(root->right) root->right = pruneTree(root->right);
if( root->val ==0 && !root->left && !root->right) return nullptr;