Practice

Table of Contents

• Data Structures
  • Array
  • String
  • Stack
  • Linked List
  • Tree
• Algorithms
  • Sort
  • Search
  • Math

Problems and Solutions

Data Structures

Array

• Find the Smallest Number
  Given an array, find the smallest number in the array.
• Find Missing Numbers
  In an array, 1-100 numbers are stored. One number is missing. How do you find it?
• Find Duplicate Numbers
  In an array of 1-100, exactly one number is duplicate. How do you find it?
• Compare Arrays
  Given two arrays, find which number(s) is not present in the second array.
• Longest Consecutive Sequence
  Given an unsorted array of integers, find the length of the longest consecutive elements sequence.
• Two Sum
  Given an array of integers, return indices of the two numbers such that they add up to a specific target.
• Remove Duplicates from Sorted Array
  Given a sorted array, remove the duplicates in place such that each element appear only once and return the new length.
• Pascal Triangle
  Given an integer x, generate the first x number of rows of Pascal’s triangle.
• Powerset
  Given an array or set of objects, return a set of all possible subsets.

String

• Remove Character
  Remove all instances of a specific character from the given String.
• String Palindrome Check
  Given a String, check if the String is a valid palindrome.
• Multiply String
  Given two numbers represented as strings, return multiplication of the numbers as a string. Do not use BigInteger.
• Merge and Order String Characters
  Given an array of strings, return a single string containing all the characters in alphabetical order.

Stack

• Array Implementation
  Includes the following methods: push(), pop(), peek(), size(), isEmpty() and isFull().
• Balanced Parentheses
  Given a String, determine if the parentheses have pairs and are in order.

Linked List

• Reverse Linked List
  Reverse a singly linked list.

Tree

• Binary Tree
  Includes methods for inserting, removing, traversing (in order, pre-order, post-order)
  and searching (find by value, smallest, nth smallest element).

Algorithms

Sort

• Quick Sort - average O(n log n); worst O(n^2)
• Merge Sort - guaranteed O(n log n)
• Insertion Sort - O(n^2)
• Bubble Sort - O(n^2)
• Selection Sort - O(n^2)

Search

• Binary Search - O(log n)
• Linear Search - O(n)

Math

• Is Prime
  Given an integer, determine whether the integer is a prime number.
• Fibonacci Sequence
  Given an integer x, print x number of elements in the sequence.
  Given an integer, return the value of the element in that position of the sequence.
• Integer Palindrome Check
  Given an integer, determine whether the integer is a valid palindrome.
• Prime Sum
  Given an even number (greater than 2), return two prime numbers whose sum will be equal to given number.
• Find Factors
  Return a list of all factors of a given integer.