Find Sum at Level K

#include<bits/stdc++.h>
using namespace std;
class node{
  public:
  int data;
  node* left;
  node* right;
  
  node(int d){
       data = d;
       left = right = NULL;
  }
};
node* buildTree(){
     int d,c;
     cin>>d>>c;
     node* root = new node(d);
     if(c==0)
     {
          
     }
     else if(c==1)
     {
          root->left = buildTree();
     }
     else if(c==2)
     {
          root->left = buildTree();
          root->right = buildTree();
     }
     return root;
     
     
}
void findSum(node* root , int k, int &sum){

     if(root==NULL)
     return;

     if(k==0){
          sum += root->data;
          return;
     }
     findSum(root->left,k-1,sum);
     findSum(root->right,k-1,sum);
     
}



int main(){
     node* root = buildTree();
     int k;
     cin>>k;
     int sum=0;
     findSum(root,k,sum);
     cout<<sum;
}