Data-Structures | Data Structures and Algorithims for Interview Preperation | Learning library

General - Find the most frequent integer in an array - Find pairs in an integer array whose sum is equal to 10 (bonus: do it in linear time) - Given 2 integer arrays, determine of the 2nd array is a rotated version of the 1st array. Trees - Implement a BST with insert and delete functions - Print a tree using BFS and DFS - Write a function that determines if a tree is a BST - Find the smallest element in a BST - Find the 2nd largest number in a BST - Given a binary tree which is a sum tree (child nodes add to parent), write an algorithm to determine whether the tree is a valid sum tree - Find the distance between 2 nodes in a BST and a normal binary tree - Print the coordinates of every node in a binary tree, where root is 0,0 - Print a tree by levels - Given a binary tree which is a sum tree, write an algorithm to determine whether the tree is a valid sum tree - Given a tree, verify that it contains a subtree. - Convert binary tree to doubly linked list - HARD: Find the max distance between 2 nodes in a BST. - HARD: Construct a BST given the pre-order and in-order traversal Strings. Stacks, Queues, and Heaps - Implement a stack with push and pop functions - Implement a queue with queue and dequeue functions - Find the minimum element in a stack in O(1) time - Write a function that sorts a stack (bonus: sort the stack in place without extra memory) - Implement a binary min heap. Turn it into a binary max heap - HARD: Implement a queue using 2 stacks. Linked Lists - Implement a linked list (with insert and delete functions) - Find the Nth element in a linked list - Remove the Nth element of a linked list - Check if a linked list has cycles - Given a circular linked list, find the node at the beginning of the loop. Sorting - Implement bubble sort - Implement selection sort - Implement insertion sort - Implement merge sort - Implement quick sort. Uncategorized - Given a max-heap, how do I find the top k items? - Find the border length created from a conglomeration of various 2D rectangles. - Write a minPeak function for a stack (function that returns the minimum element in the stack). - Find the nth fib number - Design a function in your favorite programming language to convert a camelCase string to all lowercase. - Implement a hashset - Given a corpus of valid words, design a function that takes a word as input and outputs all valid anagrams of that word. - Given an input of a 3D matrix of ones and zeros, count the number of contiguous 1-filled regions (as separated by 0-filled regions), as well as the size of the largest one (I think; doesn’t really change the problem much). - You have two sets. How would you know that they converge. - Given a bag of nuts and a bag of bolts, each having a different size within a bag but exactly one match in the other bag, give a fast algorithm to find all matches - Preorder traversal without recursion - Find the largest possible difference in an array of integers, such that the smaller integer occurs earlier in the array. - How to find if n numbers in a list sum up to an integer k? - Find largest palindrome in string - Make an anagram solver that returns all valid dictionary words given a set of characters. - Sort a string by the order it’s characters appear in another string - Given a value k and an array , design an efficient algorithm that should output the number of pairs that sum up to k. - How do you find three numbers that sum to 0? (in a list). Now can you do it under O(n^3)? - Given a Fibonacci number, tell us which index it occurs at. - Describe an algorithm that would find n numbers in a list that sum to 0. - Given an array of n unsorted ints, with the condition that each number is at most k positions away from its final sorted position, give an efficient sorting algorithm - Give an efficient solution for subset sum. - Given two (i,j) coordinates of a cell in two dimensional matrix. These coordinates are the lower left and upper right corner of a rectangle contained within the matrix. Sum all the elements in the matrix. Time and space? - String has all unique characters - Two strings to see if one is a permutation - Remove dups from an unsorted linked list - Find kth algorithm of singly linked list - Delete a node in the middle of a singly linked list given access to that node - Write code to partition a linked list around a value x such that all nodes less than x come before all nodes greater than or equal to x - Single array to implement three stacks - Stack with min element - Towers of Hanoi - Queue using two stacks - Sort a stack in ascending order using at most one additional stack to hold items but you may not copy the elements into any other data structure - Function to see if a tree is balanced - Graph algorithm, route between two nodes - Create bst from sorted array with minimal height - Binary tree is a bst - A child is running up a staircase with n steps, and cah hop either 1 step, 2 steps, or 3 steps at a time. Implement a method to count how many possible ways the child can run up the stairs - Two sorted arrays, A has a large enough buffer at the end to hold B, merge B into A in sorted order - Write a method to sort an array of strings so that all the anagrams are next to each other - Find an element in a sorted array that has been rotated an unknown number of times - Implement a method that returns true if the edit distance between two strings is less than 2 (1 or 0) or false otherwise - Given two lists of chars, return the first with removed characters that appear in the second list.