Pair_Sum_in_Binary_Search_Tree.cpp

//{ Driver Code Starts
#include <bits/stdc++.h>
using namespace std;
#define MAX_HEIGHT 100000
#define MAX_SIZE 100000

// Tree Node
struct Node
{
    int data;
    Node *left;
    Node *right;

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

// Function to Build Tree
Node *buildTree(string str)
{
    // Corner Case
    if (str.length() == 0 || str[0] == 'N')
        return NULL;

    // Creating vector of strings from input
    // string after spliting by space
    vector<string> ip;

    istringstream iss(str);
    for (string str; iss >> str;)
        ip.push_back(str);

    // Create the root of the tree
    Node *root = new Node(stoi(ip[0]));

    // Push the root to the queue
    queue<Node *> queue;
    queue.push(root);

    // Starting from the second element
    int i = 1;
    while (!queue.empty() && i < ip.size())
    {

        // Get and remove the front of the queue
        Node *currNode = queue.front();
        queue.pop();

        // Get the current node's value from the string
        string currVal = ip[i];

        // If the left child is not null
        if (currVal != "N")
        {

            // Create the left child for the current node
            currNode->left = new Node(stoi(currVal));

            // Push it to the queue
            queue.push(currNode->left);
        }

        // For the right child
        i++;
        if (i >= ip.size())
            break;
        currVal = ip[i];

        // If the right child is not null
        if (currVal != "N")
        {

            // Create the right child for the current node
            currNode->right = new Node(stoi(currVal));

            // Push it to the queue
            queue.push(currNode->right);
        }
        i++;
    }

    return root;
}

// } Driver Code Ends
/*Complete the function below
Node is as follows
struct Node {
    int data;
    Node *left;
    Node *right;

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

class Solution
{
public:
    // root : the root Node of the given BST
    // target : the target sum
    vector<int> ans;
    void inorder(struct Node *root)
    {
        if (root == NULL)
            return;
        inorder(root->left);
        ans.push_back(root->data);
        inorder(root->right);
    }
    int isPairPresent(struct Node *root, int target)
    {
        inorder(root);
        int i = 0;
        int j = ans.size() - 1;
        int sum = 0;

        while(i < j)
        {
            sum = ans[i] + ans[j];
            if (sum == target)
                return 1;
            else if (sum > target)
                j--;
            else
                i++;
        }
        return 0;
    }
};

//{ Driver Code Starts.
int main()
{

    int t;
    string tc;
    getline(cin, tc);
    t = stoi(tc);
    while (t--)
    {
        string s;
        getline(cin, s);
        Node *root = buildTree(s);

        getline(cin, s);
        int k = stoi(s);
        // getline(cin, s);
        Solution obj;
        cout << obj.isPairPresent(root, k) << endl;
        // cout<<"~"<<endl;
    }
    return 0;
}

// } Driver Code Ends