Algorithms

Question 1

Fizzbuzz

Answer 1

Print Numbers 1 to N. If a Number is divisible by 3 print fizz, if a number is divisible by 5 print buzz, if a number is divisible by 15 print fizz buzz

Question 2

Pascals Triangle

Answer 2

Triangle of rows of arrays where each cell is the sum of the two cells above it

Question 3

Needle in Haystack

Answer 3

Return the index where needle starts in haystack if it is a substring

Question 4

Pivot Index of Array

Answer 4

Return the index where the sum of the left is equal to the sum of the right

Question 5

Fibonacci w Memoization

Answer 5

Return the nth fib digit in linear time

Question 6

Reverse a LL

Answer 6

single or double

Question 7

SLL

Answer 7

push, pop, get(index), insert(index, val), delete(index)

Question 8

DLL

Answer 8

push, pop, get(index), insert(index, val), delete(index)

Question 9

Binary Search Tree

Answer 9

Insert(val), find(val)

Question 10

Merge Sort

Answer 10

Merge function O(n+m), sort O(logn)

Question 11

Quick Sort

Answer 11

O(nlogn)

Question 12

Stack

Answer 12

LIFO

Question 13

Binary Heap

Answer 13

Min or Max, compact as possible, all left children are filled, then all right children are filled

Question 14

Priority Queue

Answer 14

Min Binary Heap w Priority for nodes

Question 15

BFS Graph Traversal

Answer 15

use a queue, shift()

Question 16

DFS Graph Traversal

Answer 16

Recursive. Explore as far down one path before visiting neighbors

Question 17

Dijktra’s Algorithm

Answer 17

shortest path between two vertices

Question 18

Capitalize Words Recursively

Answer 18

Given an array of words, return the same array with the words capitalized

Question 19

Hash Table

Answer 19

hash function, Map(), separate chaining

Question 20

Queue

Answer 20

FIFO

Question 21

Graph

Answer 21

add/remove vertex, add/remove edge

Question 22

Binary Search Iterative/Recursive

Answer 22

Iterative/Recursive

Question 23

Trie

Answer 23

Trie

Question 24

Validate BST

Answer 24

recursively

Question 25

Staircase Problem

Answer 25

recursively

Question 26

Search a 2D Matrix

Answer 26

Integers in each row are sorted in ascending from left to right.
Integers in each column are sorted in ascending from top to bottom.

Question 27

Merge 2 sorted linked lists

Answer 27

similar to merging two sorted arrays

Question 28

Deserialize BST

Answer 28

construct BST from a string or array

Question 29

Is BST Balanced?

Answer 29

abs value of difference in height between subtrees <=1

Question 30

Lowest common ancestor for a BST

Answer 30

given root, x node, y node

Question 31

Serialize BST

Answer 31

given BST, construct a string

Question 32

Find Min area of rectangle given array of points

Answer 32

use a hashmap, find diagonals, calculate area

Question 33

Unique BST given n

Answer 33

Cartesean Numbers F(i,n) = G(i-1) * G(n-i)

Question 34

Level Order Traversal of BST

Answer 34

use BFS