SumOfNodesAtKthLevel-BT.cpp

// Q) Create a binary tree and display the sum of nodes upto Kth level where K is an integer value which will be provided by user.

// sagar-maheshwari653

#include <iostream>
#include <queue>
using namespace std;
struct Node
{
    int data;
    struct Node *left;
    struct Node *right;

    Node(int val)
    {
        data = val;
        left = NULL;
        right = NULL;
    }
};

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

void printLevelOrder(Node *root)
{
    if (root == NULL)
    {
        return;
    }
    queue<Node *> q;
    q.push(root);
    q.push(NULL);
    while (!q.empty())
    {
        Node *node = q.front();
        q.pop();
        if (node != NULL)
        {
            cout << node->data << " ";
            if (node->left)
            {
                q.push(node->left);
            }
            if (node->right)
            {
                q.push(node->right);
            }
        }
        else if (!q.empty())
        {
            q.push(NULL);
        }
    }
}

int sumAtK(Node* root, int k){
     if (root == NULL)
    {
        return -1;
    }
    queue<Node *> q;
    q.push(root);
    q.push(NULL);
    int level =0;
    int sum =0;
    while (!q.empty())
    {
        Node* node = q.front();
        q.pop();
        if(node!=NULL){
            if(level==k){
            sum+=node->data;
            }
            if (node->left)
            {
                q.push(node->left);
            }
            if (node->right)
            {
                q.push(node->right);
            }
            
        }else if (!q.empty())
        {
            q.push(NULL);
            level++;
        }
    }
    return sum;
}

int main()
{
    Node *root=new Node(1);

    root->left = new Node(2);
    root->right = new Node(3);
    root->left->left = new Node(4);
    root->left->right = new Node(5);
    root->right->left = new Node(6);
    root->right->right = new Node(7);

    // cout << "Inorder: ";
    // inorder(root);
   
    // printLevelOrder(root);
    cout<<sumAtK(root,2);

    return 0;
}