You are given a list of daily temperatures. For each day, you need to figure out how many days you must wait until the temperature becomes warmer. If there’s no future day with a warmer temperature, just put 0 for that day. The result will be a new list showing…

The “Remove Nth Node From End of List” problem asks you to remove the nth node from the end of a singly linked list. Think of it as counting backwards in a list of items and removing the specific one you’re pointing at. This involves understanding how to traverse and…

The “Generate Parentheses” problem is about creating all possible valid combinations of n pairs of parentheses. This problem is more about creativity and structure than raw computation—it involves figuring out how to place opening and closing parentheses such that the resulting sequence is valid. In order for sequences to be…

The Zigzag Conversion problem is all about rearranging a string into a zigzag pattern across several rows and then reading it line by line to create a new string. 2. Read row by row 3. Resulting string Optimal Algorithm: Row-by-Row Construction with Constant Space • Pattern: Simulated row traversal. •…

The “Word Pattern” problem involves checking if a given pattern string matches a sequence of words. Each character in the pattern corresponds to a word in the sequence, and the mapping between them must be consistent: no two characters can map to the same word, and no character can map…

The Search a 2D Matrix problem involves finding a target value. The matrix has two key properties: This structure makes the matrix conceptually similar to a 1D sorted array. The goal is to determine if the target exists in the matrix efficiently. Brute Force Approach Optimal Approach: Binary Search Algorithmic…

The Majority Element problem asks you to find the element that appears more than n/2 times in an array of size n. This element is guaranteed to exist. For example, in the array [3, 3, 4, 2, 3, 3, 5, 3], the majority element is 3 because it appears more…

The Remove Duplicates from Sorted Array problem asks us to take a sorted array of integers and remove duplicate values in-place so that each unique value appears only once. The result must use the initial part of the array to store unique elements, and the rest of the array beyond…

You’re given a binary tree, which is a structure where every node has at most two child nodes (left and right). Your task is to check if this tree is a Binary Search Tree. To be a valid BST, the tree must follow these rules: Think of it as ensuring…

Imagine you are hiking on a mountain trail, where the path first climbs up to a peak and then descends. To check if the trail is a “valid mountain”, the path must strictly go up and then strictly go down, with no flat or repeated sections. This problem determines whether…