3 TEST CASES SHOWING WRONG OUT OF 4

#1

#include
using namespace std;

class node
{
public:
int data;
node *left;
node *right;

node(int d)
{
    data=d;
    left=NULL;
    right=NULL;
}

};

node * buildtree()
{
int a,b;
cin>>a>>b;
node *root=new node(a);

if(b==0)
  return root;

if(root==NULL)
   return NULL;

root->left=buildtree();
root->right=buildtree();
return root;

}

int sum_at_k_level(node *root,int k)
{
static int sum=0;

if(root==NULL)
   return 0;

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

}

int main()
{
node *root=buildtree();
int k;
cin>>k;
cout<<sum_at_k_level(root,2);
}