The problem is simple to understand but great for practicing recursion. Each digit from 2 to 9 represents a set of letters, similar to the keys on a traditional phone keypad. For example, 2 maps to abc and 3 maps to def. For the input "23", the expected combinations are: ["ad","ae","af","bd","be","bf","cd","ce","cf"] 💡 Approach I first created a phoneMap object to store the letter mapping for eac…

Today I worked on the Valid Parentheses problem, a classic problem that tests stack-based problem-solving and logical thinking. The goal is simple: determine whether a string containing (), {}, and [] is valid. A string is valid when every opening bracket has the correct closing bracket, and the brackets are properly nested. I solved this using a Stack in JavaScript. Whenever an opening bracket a…

Today’s challenge was to find the longest common prefix shared by all strings in an array. I implemented the solution in JavaScript and successfully passed all 126 test cases. The approach is straightforward and easy to understand. I started with the first string as the reference and compared each of its characters with the corresponding character in every other string. If a character does not ma…

The problem looks simple at first, but it is a great example of how choosing the right data structure can make a solution both clean and efficient. The goal is to determine whether a string containing (), {}, and [] is valid. Every opening bracket must have the correct closing bracket, and brackets must close in the proper order. I solved it using a Stack. The approach is straightforward: Create …

Today I solved LeetCode 21: Merge Two Sorted Lists, a classic linked-list problem that is great for strengthening pointer manipulation and understanding how linked lists work. The goal is simple: given two sorted linked lists, merge them into a single sorted linked list. For example: Input: List 1: [1,2,4] List 2: [1,3,4] Output: [1,1,2,3,4,4] I solved this using a dummy node and a current pointe…