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Kth largest element in BST.cpp
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Kth largest element in BST.cpp
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//{ Driver Code Starts
#include <bits/stdc++.h>
using namespace std;
// 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
/*The Node structure is defined as
struct Node {
int data;
Node *left;
Node *right;
Node(int val) {
data = val;
left = right = NULL;
}
};
*/
// return the Kth largest element in the given BST rooted at 'root'
class Solution
{
public:
int ans;
void dfs(Node *root, int &k)
{
if (root == NULL)
return;
dfs(root->right, k);
k--;
if (k == 0)
{
ans = root->data;
return;
}
dfs(root->left, k);
}
int kthLargest(Node *root, int k)
{
// Your code her
dfs(root, k);
return ans;
}
};
//{ Driver Code Starts.
int main()
{
int t;
cin >> t;
getchar();
while (t--)
{
string s;
getline(cin, s);
Node *head = buildTree(s);
int k;
cin >> k;
getchar();
Solution ob;
cout << ob.kthLargest(head, k) << endl;
}
return 1;
}
// } Driver Code Ends