Rahul's BaseCS

Rahul Saxena

Rahul Saxena

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All about my learnings in the CS & Software Engineering World. Currently, sharing my solutions to popular coding questions with occasional notes on System Design.

1699. Number of Calls Between Two Persons

Dec 28, 20222 min read

Asked in: Facebook, Amazon. Table: Calls +-------------+---------+ | Column Name | Type | +-------------+---------+ | from_id | int | |...

1699. Number of Calls Between Two Persons

Slow and Fast Pointers: 234. Palindrome Linked List

Jun 25, 20222 min read

Question: Given the head of a singly linked list, return true if it is a palindrome. Example 1: Input: head = [1,2,2,1] Output: true Example 2: Input:...

Slow and Fast Pointers: 234. Palindrome Linked List

Leetcode 75: 102. Binary Tree Level Order Traversal

Jun 25, 20223 min read

Question: Given the root of a binary tree, return the level order traversal of its nodes' values. (i.e., from left to right, level by level). Example...

Leetcode 75: 102. Binary Tree Level Order Traversal

202. Happy Number

Jun 19, 20222 min read

Question: Write an algorithm to determine if a number n is happy. A happy number is a number defined by the following process: Starting with any...

202. Happy Number

Pattern: Slow and Fast Pointers

Jun 19, 20221 min read

It's a pointer algorithm that involves two pointers that move through the Array or LinkedList at different speeds. It's also known as Hare and...

Pattern: Slow and Fast Pointers

Leetcode 75: Day 4: 142. Linked List Cycle II

Jun 19, 20222 min read

Question: Given the head of a linked list, return the node where the cycle begins. If there is no cycle, return null. There is a cycle in a linked...

Leetcode 75: Day 4: 142. Linked List Cycle II