Flatten Binary Tree to Linked List LeetCode Programming Solutions | LeetCode Problem Solutions in C++, Java, & Python [💯Correct]

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Hello Programmers/Coders, Today we are going to share solutions to the Programming problems of LeetCode Solutions in C++, Java, & Python. At Each Problem with Successful submission with all Test Cases Passed, you will get a score or marks and LeetCode Coins. And after solving maximum problems, you will be getting stars. This will highlight your profile to the recruiters.

In this post, you will find the solution for the Flatten Binary Tree to Linked List in C++, Java & Python-LeetCode problem. We are providing the correct and tested solutions to coding problems present on LeetCode. If you are not able to solve any problem, then you can take help from our Blog/website.

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About LeetCode

LeetCode is one of the most well-known online judge platforms to help you enhance your skills, expand your knowledge and prepare for technical interviews. 

LeetCode is for software engineers who are looking to practice technical questions and advance their skills. Mastering the questions in each level on LeetCode is a good way to prepare for technical interviews and keep your skills sharp. They also have a repository of solutions with the reasoning behind each step.

LeetCode has over 1,900 questions for you to practice, covering many different programming concepts. Every coding problem has a classification of either EasyMedium, or Hard.

LeetCode problems focus on algorithms and data structures. Here is some topic you can find problems on LeetCode:

  • Mathematics/Basic Logical Based Questions
  • Arrays
  • Strings
  • Hash Table
  • Dynamic Programming
  • Stack & Queue
  • Trees & Graphs
  • Greedy Algorithms
  • Breadth-First Search
  • Depth-First Search
  • Sorting & Searching
  • BST (Binary Search Tree)
  • Database
  • Linked List
  • Recursion, etc.

Leetcode has a huge number of test cases and questions from interviews too like Google, Amazon, Microsoft, Facebook, Adobe, Oracle, Linkedin, Goldman Sachs, etc. LeetCode helps you in getting a job in Top MNCs. To crack FAANG Companies, LeetCode problems can help you in building your logic.

Link for the ProblemFlatten Binary Tree to Linked List– LeetCode Problem

Flatten Binary Tree to Linked List– LeetCode Problem

Problem:

Given the root of a binary tree, flatten the tree into a “linked list”:

  • The “linked list” should use the same TreeNode class where the right child pointer points to the next node in the list and the left child pointer is always null.
  • The “linked list” should be in the same order as a pre-order traversal of the binary tree.

Example 1:

flaten
Input: root = [1,2,5,3,4,null,6]
Output: [1,null,2,null,3,null,4,null,5,null,6]

Example 2:

Input: root = []
Output: []

Example 3:

Input: root = [0]
Output: [0]

Constraints:

  • The number of nodes in the tree is in the range [0, 2000].
  • -100 <= Node.val <= 100
Flatten Binary Tree to Linked List– LeetCode Solutions
Flatten Binary Tree to Linked List Solution in C++:
class Solution {
 public:
  void flatten(TreeNode* root) {
    if (!root)
      return;

    flatten(root->left);
    flatten(root->right);

    TreeNode* const left = root->left;    // flattened left
    TreeNode* const right = root->right;  // flattened right

    root->left = nullptr;
    root->right = left;

    // connect the original right subtree
    // to the end of new right subtree
    TreeNode* rightmost = root;
    while (rightmost->right)
      rightmost = rightmost->right;
    rightmost->right = right;
  }
};
Flatten Binary Tree to Linked List Solution in Java:
class Solution {
  public void flatten(TreeNode root) {
    if (root == null)
      return;

    while (root != null) {
      if (root.left != null) {
        // find the rightmost root
        TreeNode rightmost = root.left;
        while (rightmost.right != null)
          rightmost = rightmost.right;
        // rewire the connections
        rightmost.right = root.right;
        root.right = root.left;
        root.left = null;
      }
      // move on to the right side of the tree
      root = root.right;
    }
  }
}
Flatten Binary Tree to Linked List Solution in Python:
class Solution {
  public void flatten(TreeNode root) {
    if (root == null)
      return;

    while (root != null) {
      if (root.left != null) {
        // find the rightmost root
        TreeNode rightmost = root.left;
        while (rightmost.right != null)
          rightmost = rightmost.right;
        // rewire the connections
        rightmost.right = root.right;
        root.right = root.left;
        root.left = null;
      }
      // move on to the right side of the tree
      root = root.right;
    }
  }
}

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