// By CHOUBIK Houssam - Time complexity O(n)
bool isSameTree(struct TreeNode* p, struct TreeNode* q) {
if(p==NULL && q==NULL){
return true;
}
if(p==NULL || q==NULL){
return false;
}
if(p->val!=q->val){
return false;
}
return isSameTree(p->left,q->left) && isSameTree(p->right,q->right);
}