replace a node with sum of its children

#include <bits/stdc++.h>
using namespace std;
class node{
    public:
    int data;
    node *left;
    node *right;
    node(int d){
        data=d;
        left=NULL;
        right=NULL;
    }
};


node* buildTree(){
    int data;
    cin>>data;
    if(data==-1)
        return NULL;
    node* curr=new node(data);
    curr->left=buildTree();
    curr->right=buildTree();
    return curr;
}

void print(node *root){
    if(root==NULL)
        return;
    print(root->left);
    print(root->right);
    cout<<root->data<<" ";
}

int replaceSum(node *root){
    if(root!=NULL&&root->left==NULL&&root->right==NULL)
        return root->data;
    if(root==NULL)
        return 0;
    // if(root->left==NULL&&root->right==NULL)
    //     return;
    int temp=root->data;
    int l=replaceSum(root->left);
    int r=replaceSum(root->right);
    root->data=l+r;
    // int l=root->left ? root->left->data : 0;
    // int r=root->right ? root->right->data : 0;
    return root->data+temp;
}

int main() {

    node *root=buildTree();
    print(root);
    replaceSum(root);
    cout<<endl;
    print(root);
    return 0;
}