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Problem Statement (Asked By Airbnb) Given a list of integers, write a function to compute the largest sum of numbers such that no two numbers are adjacent in the list. The input may contain zero or negative values. For example, [2, 4, 6, 2, 5] should return 13, since we pick 2, 6, and 5. [5, 1, 1, 5] should return 10, since we […]
A unival tree (short for “universal value tree”) is a tree in which all nodes have the same value.
Given the root of a binary tree, determine how many unival subtrees it contains.
For example, the following tree has 5 unival subtrees:
January 6, 2025 | Binary Tree, dsa, DSA Sheet, Google | No comments
Problem Statement (Asked By Facebook) Given the mapping a = 1, b = 2, …, z = 26, and an encoded message, count the number of possible ways to decode it. For example, the message ‘111’ would give 3, since it could be decoded as ‘aaa’, ‘ka’, and ‘ak’. You can assume that the messages […]
January 5, 2025 | DP, dsa, DSA Sheet, Facebook | No comments
An XOR-linked list is a memory-efficient version of a doubly linked list. Instead of each node storing separate next and prev pointers, each node contains a single field called both, which stores the result of the XOR operation on the memory addresses of the next and previous nodes.
Problem Statement (Asked By Jane Street) The function cons(a, b) creates a pair of two elements. Implement two functions: For instance: Below is the implementation of cons: Your task is to define the car and cdr functions. Disclaimer: Try solving the problem on your own first! Use this solution only as a reference to learn and […]
January 3, 2025 | dsa, DSA Sheet, Jane Street | No comments
Problem Statement (Asked By Stripe) You are given an array of integers. Your task is to find the smallest missing positive integer in O(N) time using O(1) additional space. In other words, identify the smallest positive number that is not present in the array. The array may include: You are allowed to modify the input […]
Given the root of a binary tree, create two functions:
serialize(root) – Converts the binary tree into a string representation.
deserialize(s) – Reconstructs the binary tree from its string representation.
January 1, 2025 | array, dsa, DSA Sheet, Google | No comments
Problem Statement (Asked By Uber) Given a list of integers, return a new list such that each element at index i of the new list is the product of all the elements in the original list except the one at i. For instance, if the input is [1, 2, 3, 4, 5], the expected output […]
December 30, 2024 | Algorithm, array, Data Structure, dsa, Uber | No comments
Problem Statement (Asked By Google) Given a list of integers and a target number k, determine if there exist two numbers in the list whose sum equals k. For example, given [10, 15, 3, 7] and k = 17, return True because 10 + 7 = 17. Bonus: Can you solve this in a single […]
Problem Statement: Given n pairs of parentheses, write a function to generate all combinations of well-formed parentheses. Example 1: Input: n = 3 Output: [“((()))”,”(()())”,”(())()”,”()(())”,”()()()”]Example 2: Input: n = 1 Output: [“()”] Solution: This problem can be solved using the concept of backtracking, Let’s see how to approach it. We have to write a function generate([], left, right, […]
September 24, 2024 | 23 DSA Patterns | No comments