230. Kth Smallest Element in a BST
A BST's inorder traversal visits nodes in ascending order. The kth node visited during inorder traversal is the kth smallest element. The recursive solution is concise and easy to understand. The iterative solution uses a stack to simulate recursion and is the standard interview approach.
LeetCode 98: Validate Binary Search Tree (Python)
Comparing a node with only its parent is not sufficient. Every node must satisfy constraints inherited from all its ancestors. Passing a valid (lower, upper) range during DFS elegantly enforces the BST rules. This is the standard interview solution and is both simple and optimal.
1448. Count Good Nodes in Binary Tree (LeetCode)
This is an excellent example of a DFS problem where the trick is not the traversal itself, but what information you carry along the path. By passing the maximum value seen so far, each node can determine independently whether it is "good," resulting in a simple and efficient O(n) solution.
199. Binary Tree Right Side View (LeetCode) – BFS Explained
Whenever a binary tree problem asks for something "per level", BFS should be one of your first thoughts. For the right side view: Traverse level by level. The last node of every level is visible from the right. Record it and continue.
LeetCode 235: Lowest Common Ancestor of a Binary Search Tree
Binary Search Trees (BSTs) are special because they allow us to make decisions without exploring every node. This problem is a great example of taking advantage of that property to find the Lowest Common Ancestor (LCA) in O(h)time instead of searching the entire tree.
572. Subtree of Another Tree – Explanation
A brute-force approach would compare subRoot against every node, which is exactly what this recursive solution does. Since each comparison uses the optimal Same Tree algorithm, this is the standard interview solution and is accepted by virtually every interviewer.
LeetCode 110: Balanced Binary Tree – Three DFS Solutions Explained
Whenever a tree problem asks you to determine something about a node based on information from its children, think post-order DFS. For this problem, every node needs: left subtree height, right subtree height, whether both subtrees are already balanced
Leetcode 104 : Maximum Depth of Binary Tree — Recursive DFS, BFS, and Iterative DFS
With recursive DFS, the answer for each node is:1 + the greater depth of its two subtrees With BFS, the answer is the number of levels processed. With iterative DFS, each node is stored together with its current depth.
226. Invert Binary Tree – Three Ways to Solve It (Recursive, DFS, and BFS)
Binary Tree problems are a staple in coding interviews, and Invert Binary Tree is one of the most famous ones. Despite its simplicity, this problem is an excellent exercise for understanding tree traversal and the differences between recursive DFS, iterative DFS, and BFS.
LeetCode 287: Find the Duplicate Number — Floyd’s Cycle Detection Explained
The duplicate creates a cycle because two indices eventually lead to the same node. Floyd’s Tortoise and Hare algorithm detects that cycle without modifying the array. Resetting one pointer to the start lets you find the cycle entrance, which is the duplicate number.
Solution: Leetcode 21 Solving the Merge Two Sorted Lists Problem in Python
You are given the heads of two sorted linked lists, list1 and list2. Merge the two lists into one sorted list. The list should be made by splicing together the nodes of the first two lists. Return the head of the merged linked list.
LeetCode 155: Min Stack – Constant Time Minimum Lookup
The key insight isn’t about finding the minimum quickly—it’s about remembering the minimum as the stack evolves. By maintaining a second stack that mirrors the main stack and stores the minimum value at every level, we eliminate the need to recompute the minimum after every pop().
Solution: Leetcode 682 Solving a Baseball Scoring Puzzle with Python
You are keeping the scores for a baseball game with a unique set of rules. At the beginning of the game, you start with an empty record. You're given a list of strings operations, where each element represents an operation to apply to the record.
Solution: Leetcode 1929 Solving the Array Concatenation Problem in Python
You are given an integer array nums of length n. The task is to create a new array ans of length 2n such that ans[i] == nums[i] and ans[i + n] == nums[i] for 0 <= i < n (0-indexed). In simpler terms, the array ans is formed by concatenating two copies of the array nums.
Solution: Leetcode 26 Removing Duplicates from Sorted Array in Python
The problem at hand is to remove duplicates from a sorted integer array nums in-place, such that each unique element appears only once. Additionally, we need to return the number of unique elements present in the modified array.
88. Merge Sorted Array – LeetCode Solution Explained Problem Link
You are given two integer arrays nums1 and nums2, sorted in non-decreasing order, and two integers m and n, representing the number of elements in nums1 and nums2 respectively. Merge nums1 and nums2 into a single array sorted in non-decreasing order.
How to - Handle Process Environment Variables in TypeScript: A Comprehensive Guide with Code
In this article, we cover various techniques for handling process environment variables in TypeScript, such as using type assertions, creating typed configuration objects, using type guards, and leveraging configuration libraries like dotenv and dotenv-safe.
How to add new Cognito users automatically to a group on sign up - AWS Cognito, Lambda
We will set up a Post Confirmation lambda trigger for adding new users automatically to a certain group. in this guide, we will implement the code for the said function, assign permissions and attach the Lambda function to the Cognito user pool.
Solved - Type 'x' is not assignable to type 'never' using TypeScript in React
This error occurs when you have not explicitly given a type to a value. Resulting in the implicit assignment of the type "never" to the value. The "never" type always expects the value to the empty and throws an error when its not empty.
Solved - Type x is missing the following properties from type y using TypeScript in React
This error occurs when you are not passing all the required props or only passing some of the required props to the component. Pass all the props or define the typing of the component accordingly to handle this error.
