Data Structure Algorithms

Arrays & Strings

• Two Sum (Given an array and a target, find indices of two numbers that add up to the target. [Google, Amazon, Facebook])
• Best Time to Buy and Sell Stock (Find the maximum profit you can achieve from a list of stock prices by choosing a single buy and sell. [Amazon, Microsoft])
• Product of Array Except Self (Return an array where each element is the product of all other elements, without using division. [Facebook, Amazon])
• Maximum Subarray (Kadane’s Algorithm) (Find the contiguous subarray with the largest sum within a one-dimensional array. [Amazon, Microsoft])
• Merge Intervals (Given a collection of intervals, merge all overlapping intervals. [Google, Apple])
• Longest Substring Without Repeating Characters (Find the length of the longest substring without repeating characters in a string. [Amazon, Microsoft])
• Rotate Array (Rotate an array to the right by k steps. [Microsoft])
• Search in Rotated Sorted Array (Search for a target value in a rotated sorted array in O(log n) time. [Google])
• Set Matrix Zeroes (If an element is 0, set its entire row and column to 0 in-place in a matrix. [Microsoft])
• Spiral Matrix (Return all elements of a matrix in spiral order. [Amazon])
• Trapping Rain Water (Given an elevation map, compute how much water it can trap after raining. [Amazon])
• Container With Most Water (Find two lines that together with the x-axis form a container, such that the container contains the most water. [Google, Amazon])
• 3Sum (Find all unique triplets in the array that give the sum of zero. [Facebook, Amazon])
• 4Sum (Find all unique quadruplets that give the sum of a target value. [Google])
• Remove Duplicates from Sorted Array (Remove duplicates in-place from a sorted array. [Microsoft])
• Find First and Last Position of Element in Sorted Array (Find the starting and ending position of a given target value. [Google])
• Search a 2D Matrix (Search for a value in an m x n matrix with sorted rows and columns. [Amazon])
• Longest Palindromic Substring (Find the longest palindromic substring in a string. [Amazon, Microsoft])
• Valid Anagram (Determine if two strings are anagrams of each other. [Facebook])
• Minimum Window Substring (Find the minimum window substring that contains all characters of another string. [Facebook])
• Group Anagrams (Group strings that are anagrams of each other. [Apple])
• String to Integer (atoi) (Implement the myAtoi(string s) function which converts a string to a 32-bit signed integer. [Amazon])
• ZigZag Conversion (Convert string into a zigzag pattern on a given number of rows. [Google])
• Reverse Words in a String (Reverse the order of words in a string. [Microsoft])
• Implement strStr() (Return the index of the first occurrence of needle in haystack. [Facebook])
• Count and Say (Generate the nth term of the count-and-say sequence. [Amazon])
• Majority Element (Find the majority element that appears more than n/2 times. [Google])
• Pascal’s Triangle (Generate the first numRows of Pascal’s triangle. [Apple])
• Plus One (Add one to a number represented as an array of digits. [Google])
• Remove Element (Remove all instances of a value from an array in-place. [Facebook])
• Find Peak Element (Find a peak element in an array (where arr[i] > arr[i-1] and arr[i] > arr[i+1]). [Microsoft])

Linked Lists

• Reverse a Linked List (Reverse a singly linked list iteratively or recursively. [Amazon, Facebook])
• Detect Cycle in a Linked List (Determine if a linked list has a cycle using constant space. [Google, Amazon])
• Merge Two Sorted Lists (Merge two sorted linked lists and return it as a new sorted list. [Amazon, Microsoft])
• Remove Nth Node From End of List (Remove the nth node from the end of a singly linked list in one pass. [Facebook])
• Add Two Numbers (Linked List) (Add two numbers represented by linked lists, where each node contains a single digit. [Google, Amazon])
• Intersection of Two Linked Lists (Find the node at which two singly linked lists intersect, if any. [Amazon])
• Copy List with Random Pointer (Deep copy a linked list where each node has a random pointer. [Facebook])
• LRU Cache (Design and implement a data structure for Least Recently Used (LRU) cache. [Amazon])
• Remove Duplicates from Sorted List (Remove all duplicates from a sorted linked list. [Facebook])
• Palindrome Linked List (Check if a linked list is a palindrome. [Amazon])
• Reverse Nodes in k-Group (Reverse nodes of a linked list k at a time. [Facebook])
• Rotate List (Rotate the list to the right by k places. [Google])
• Partition List (Partition a linked list around a value x. [Microsoft])
• Sort List (Sort a linked list using constant space complexity. [Amazon])
• Flatten a Multilevel Doubly Linked List (Flatten a multilevel doubly linked list. [Amazon])
• Delete Node in a Linked List (Delete a node in a linked list given only access to that node. [Apple])
• Odd Even Linked List (Group all odd nodes together followed by the even nodes. [Amazon])

Stacks & Queues

• Valid Parentheses (Check if a string containing just the characters ‘(’, ‘)’, ‘{’, ‘}’, ‘[’ and ‘]’ is valid. [Facebook, Amazon])
• Min Stack (Design a stack that supports push, pop, top and retrieving the minimum element in constant time. [Amazon])
• Evaluate Reverse Polish Notation (Evaluate the value of an arithmetic expression in Reverse Polish Notation. [Google])
• Daily Temperatures (Given a list of daily temperatures, return a list that tells how many days to wait until a warmer temperature. [Amazon])
• Implement Queue using Stacks (Implement a queue using two stacks. [Microsoft])
• Sliding Window Maximum (Find the maximum value in each sliding window of size k in an array. [Amazon])
• Next Greater Element (For each element in an array, find the next greater element to its right. [Google])
• Largest Rectangle in Histogram (Find the area of the largest rectangle in a histogram. [Amazon])
• Maximal Rectangle (Find the maximal rectangle containing only 1s in a binary matrix. [Google])
• Remove K Digits (Remove k digits from a number to make it smallest. [Google])
• Asteroid Collision (Simulate the collision of asteroids in a row. [Facebook])
• Basic Calculator (Implement a basic calculator to evaluate a simple expression string. [Google])
• Simplify Path (Simplify an absolute path for a file in a Unix-style file system. [Facebook])
• Decode String (Decode a string encoded with a specific pattern. [Amazon])
• Implement Stack using Queues (Implement a stack using two queues. [Microsoft])
• Moving Average from Data Stream (Calculate the moving average of all integers in a sliding window. [Google])

Trees & Graphs

• Binary Tree Traversal (Inorder/Preorder/Postorder) (Traverse a binary tree in different orders recursively or iteratively. [Amazon, Microsoft])
• Level Order Traversal (BFS) (Return the level order traversal of a binary tree’s nodes’ values. [Facebook])
• Maximum Depth of Binary Tree (Find the maximum depth (height) of a binary tree. [Amazon])
• Validate Binary Search Tree (Check if a binary tree is a valid binary search tree. [Google])
• Lowest Common Ancestor (Find the lowest common ancestor of two nodes in a binary tree. [Facebook])
• Serialize and Deserialize Binary Tree (Convert a binary tree to a string and back. [Google])
• Number of Islands (Given a 2D grid, count the number of islands (connected groups of 1s). [Amazon, Facebook])
• Clone Graph (Clone an undirected graph with possible cycles. [Facebook])
• Word Ladder (Find the shortest transformation sequence from beginWord to endWord, changing one letter at a time. [Google])
• Course Schedule (Topological Sort) (Determine if you can finish all courses given prerequisites. [Google])
• Diameter of Binary Tree (Find the length of the longest path between any two nodes in a binary tree. [Amazon])
• Same Tree (Check if two binary trees are the same. [Google])
• Symmetric Tree (Check whether a binary tree is a mirror of itself. [Microsoft])
• Path Sum (Check if there is a path from root to leaf with a given sum. [Amazon])
• Minimum Depth of Binary Tree (Find the minimum depth of a binary tree. [Facebook])
• Flatten Binary Tree to Linked List (Flatten a binary tree to a linked list in-place. [Microsoft])
• Populating Next Right Pointers (Connect each node to its next right node in the same level. [Facebook])
• Binary Tree Maximum Path Sum (Find the maximum path sum in a binary tree. [Amazon])
• Construct Binary Tree from Preorder and Inorder (Construct binary tree from preorder and inorder traversal. [Google])
• Kth Smallest Element in BST (Find the kth smallest element in a BST. [Google])
• Binary Search Tree Iterator (Implement an iterator over a BST in sorted order. [Facebook])
• Recover Binary Search Tree (Recover a BST where exactly two nodes were swapped by mistake. [Amazon])
• Word Search II (Find all words in a board using a trie. [Google])
• Alien Dictionary (Find the order of characters in an alien language. [Google])
• Graph Valid Tree (Check if a graph forms a valid tree. [Facebook])
• Number of Connected Components (Find the number of connected components in an undirected graph. [Google])
• Pacific Atlantic Water Flow (Find cells from which water can flow to both Pacific and Atlantic oceans. [Google])
• Cheapest Flights Within K Stops (Find the cheapest price to travel with at most k stops. [Amazon])
• Network Delay Time (Find the time for all nodes to receive signal from a source. [Google])
• Reconstruct Itinerary (Reconstruct the itinerary from a list of airline tickets. [Google])

Heaps & Priority Queues

• Merge K Sorted Lists (Merge k sorted linked lists into one sorted list. [Google])
• Find Median from Data Stream (Continuously find the median as numbers are added to a stream. [Google])
• Top K Frequent Elements (Return the k most frequent elements in an array. [Amazon])
• Kth Largest Element in an Array (Find the kth largest element in an unsorted array. [Amazon])
• Sliding Window Median (Find the median of each sliding window of size k. [Google])
• Find K Pairs with Smallest Sums (Find k pairs with smallest sums from two arrays. [Google])
• Ugly Number II (Find the nth ugly number (only factors of 2, 3, 5). [Amazon])
• Super Ugly Number (Find the nth super ugly number given a list of prime factors. [Google])
• Meeting Rooms II (Find the minimum number of conference rooms required. [Facebook])
• Task Scheduler (Find the minimum time needed to execute all tasks with cooldown. [Facebook])
• Reorganize String (Reorganize string so that no two same characters are adjacent. [Google])
• K Closest Points to Origin (Find the k closest points to the origin. [Amazon])
• Kth Smallest Element in a Sorted Matrix (Find the kth smallest element in a sorted matrix. [Google])

Hashing

• Group Anagrams (Group strings that are anagrams of each other. [Apple])
• Longest Consecutive Sequence (Find the length of the longest consecutive elements sequence in an unsorted array. [Facebook])
• Subarray Sum Equals K (Count the number of subarrays whose sum equals k. [Amazon])
• Isomorphic Strings (Determine if two strings are isomorphic (characters can be replaced to get the other). [Microsoft])
• Word Pattern (Check if a string follows the same pattern as a pattern string. [Google])
• Contains Duplicate (Check if array contains any duplicates. [Amazon])
• Contains Duplicate II (Check if there are duplicates within k distance. [Google])
• Happy Number (Determine if a number is happy. [Facebook])
• First Unique Character in String (Find the first non-repeating character in a string. [Amazon])
• Find All Anagrams in String (Find all start indices of anagrams of p in s. [Facebook])
• Minimum Window Substring (Find minimum window that contains all characters of another string. [Facebook])
• Longest Substring with At Most K Distinct Characters (Find longest substring with at most k distinct characters. [Google])
• Frequency of Most Frequent Element (Find frequency of the most frequent element after k operations. [Google])
• Design HashMap (Design a HashMap without using built-in libraries. [Amazon])
• Design HashSet (Design a HashSet without using built-in libraries. [Facebook])

Recursion & Backtracking

• Subsets (Return all possible subsets (the power set) of a set of numbers. [Facebook])
• Permutations (Return all possible permutations of a list of numbers. [Google])
• Combination Sum (Find all unique combinations that sum up to a target, with unlimited use of numbers. [Amazon])
• Word Search (Given a 2D board and a word, check if the word exists in the board. [Facebook])
• Sudoku Solver (Solve a Sudoku puzzle by filling the empty cells. [Google])
• N-Queens (Place n queens on an n×n chessboard so that no two queens threaten each other. [Amazon])
• Combination Sum II (Find all unique combinations that sum to target, each number used once. [Google])
• Combinations (Return all possible combinations of k numbers out of 1…n. [Microsoft])
• Letter Combinations of Phone Number (Return all possible letter combinations from a phone number. [Amazon])
• Palindrome Partitioning (Partition a string such that every substring is a palindrome. [Google])
• Restore IP Addresses (Restore valid IP addresses from a string of digits. [Facebook])
• Word Break II (Add spaces to segment string into words from dictionary. [Google])
• Unique Paths III (Count unique paths visiting every empty square exactly once. [Google])
• Expression Add Operators (Add binary operators to get target value. [Google])
• Remove Invalid Parentheses (Remove minimum invalid parentheses to make valid. [Facebook])
• Generalized Abbreviation (Generate all possible abbreviations of a word. [Google])

Dynamic Programming

• Climbing Stairs (Count the number of distinct ways to climb to the top of a staircase with n steps. [Amazon])
• Coin Change (Find the minimum number of coins needed to make up a given amount. [Google])
• Longest Increasing Subsequence (Find the length of the longest increasing subsequence in an array. [Amazon])
• Longest Common Subsequence (Find the length of the longest common subsequence between two strings. [Facebook])
• Edit Distance (Compute the minimum number of operations to convert one string to another. [Google])
• House Robber (Find the maximum amount of money you can rob without robbing adjacent houses. [Amazon])
• Maximum Product Subarray (Find the contiguous subarray within an array which has the largest product. [Amazon])
• Decode Ways (Count the number of ways to decode a string of digits. [Facebook])
• Unique Paths (Count the number of unique paths from top-left to bottom-right in a grid. [Google])
• Palindromic Substrings (Count how many substrings in a string are palindromes. [Amazon])
• Partition Equal Subset Sum (Determine if an array can be partitioned into two subsets with equal sum. [Facebook])
• House Robber II (Rob houses arranged in a circle. [Google])
• Best Time to Buy and Sell Stock with Cooldown (Buy and sell stock with cooldown period. [Google])
• Word Break (Check if string can be segmented into words from dictionary. [Amazon])
• Coin Change 2 (Find number of ways to make amount with given coins. [Facebook])
• Target Sum (Find number of ways to assign +/- to reach target sum. [Google])
• Delete Operation for Two Strings (Find minimum steps to make two strings the same by deleting characters. [Google])
• Minimum Path Sum (Find path with minimum sum from top-left to bottom-right. [Amazon])
• Triangle (Find minimum path sum from top to bottom of triangle. [Amazon])
• Maximum Length of Repeated Subarray (Find maximum length of subarray that appears in both arrays. [Google])
• Russian Doll Envelopes (Find maximum number of envelopes you can put inside each other. [Google])
• Burst Balloons (Find maximum coins you can collect by bursting balloons. [Google])
• Stone Game (Determine if first player can win the stone game. [Amazon])
• Regular Expression Matching (Implement regex matching with ‘.’ and ‘*’. [Google])
• Wildcard Matching (Implement wildcard pattern matching with ‘?’ and ‘*’. [Google])
• Interleaving String (Check if s3 is formed by interleaving s1 and s2. [Facebook])
• Distinct Subsequences (Count distinct subsequences of s in t. [Google])
• Scramble String (Check if one string is a scrambled string of another. [Google])

Greedy Algorithms

• Jump Game (Determine if you can reach the last index of the array given max jump lengths. [Google])
• Gas Station (Given gas and cost at each station, find if you can complete the circuit. [Google])
• Candy Distribution (Distribute candies to children such that each child has at least one and those with higher ratings get more. [Amazon])
• Interval Scheduling (Meeting Rooms) (Find the minimum number of meeting rooms required for all meetings. [Google])
• Minimum Number of Platforms (Find the minimum number of platforms needed for trains so that no train waits. [Amazon])
• Jump Game II (Find minimum number of jumps to reach the end. [Amazon])
• Non-overlapping Intervals (Find minimum number of intervals to remove to make rest non-overlapping. [Facebook])
• Partition Labels (Partition string into as many parts as possible. [Amazon])
• Queue Reconstruction by Height (Reconstruct queue based on height and number of taller people. [Google])
• Minimum Cost to Connect Sticks (Find minimum cost to connect all sticks. [Amazon])
• Task Scheduler (Find minimum time to execute all tasks with cooldown. [Facebook])
• Remove Duplicate Letters (Remove duplicate letters so result is smallest in lexicographical order. [Google])
• Monotone Increasing Digits (Find largest number smaller than N with monotone increasing digits. [Google])
• Lemonade Change (Check if you can provide correct change to all customers. [Amazon])
• Assign Cookies (Assign cookies to children to maximize number of content children. [Google])

Bit Manipulation

• Single Number (Find the element that appears only once in an array where every other appears twice. [Google])
• Counting Bits (For every number i, return the number of 1’s in its binary representation. [Facebook])
• Reverse Bits (Reverse the bits of a given 32 bits unsigned integer. [Microsoft])
• Missing Number (Find the missing number in an array containing n distinct numbers from 0 to n. [Amazon])
• Sum of Two Integers (without + or -) (Calculate the sum of two integers without using + or -. [Facebook])
• Power of Two (Check if a number is a power of two. [Google])
• Power of Four (Check if a number is a power of four. [Google])
• Number of 1 Bits (Count the number of 1 bits in an integer. [Amazon])
• Bitwise AND of Numbers Range (Find bitwise AND of all numbers in a range. [Google])
• Single Number III (Find two numbers that appear only once in an array. [Facebook])
• Maximum XOR of Two Numbers (Find maximum XOR of any two numbers in array. [Google])
• Repeated DNA Sequences (Find repeated DNA sequences of length 10. [Amazon])
• Gray Code (Generate Gray code sequence. [Google])
• Minimum XOR Sum of Two Arrays (Find minimum XOR sum after rearranging one array. [Google])
• Find the Duplicate Number (Find duplicate in array with numbers 1 to n. [Microsoft])

Math & Miscellaneous

• Sieve of Eratosthenes (Generate all prime numbers up to a given number n. [Google])
• Pow(x, n) (Implement x raised to the power n (x^n). [Facebook])
• Excel Sheet Column Number (Convert an Excel column title (e.g., “AB”) to its corresponding column number. [Microsoft])
• Roman to Integer (Convert a Roman numeral to an integer. [Amazon])
• Integer to English Words (Convert a non-negative integer to its English words representation. [Google])
• Sqrt(x) (Compute and return the square root of x. [Facebook])
• Valid Number (Check if a string is a valid number. [Google])
• Multiply Strings (Multiply two non-negative integers represented as strings. [Facebook])
• Add Binary (Add two binary strings and return their sum. [Facebook])
• Factorial Trailing Zeroes (Count trailing zeroes in n!. [Amazon])
• Count Primes (Count number of prime numbers less than n. [Amazon])
• Happy Number (Determine if a number is happy. [Google])
• Ugly Number (Check if a number is ugly (only factors 2, 3, 5). [Facebook])
• Perfect Squares (Find least number of perfect squares that sum to n. [Google])
• Integer Break (Break integer n into sum of positive integers to maximize product. [Google])
• Water and Jug Problem (Determine if you can measure exactly z liters using jugs of capacity x and y. [Microsoft])
• Nth Digit (Find the nth digit in the sequence 1,2,3,4,5,6,7,8,9,10,11… [Google])
• Palindrome Number (Check if an integer is a palindrome. [Amazon])
• Reverse Integer (Reverse digits of a 32-bit signed integer. [Apple])
• Plus One (Add one to a number represented as array of digits. [Google])
• Excel Sheet Column Title (Convert a positive integer to its Excel column title. [Microsoft])
• Fractions to Recurring Decimal (Convert fraction to decimal, handle recurring decimals. [Google])

Two Pointers

• Two Sum II - Input array is sorted (Find two numbers in sorted array that add up to target. [Amazon])
• 3Sum Closest (Find three integers whose sum is closest to target. [Facebook])
• Remove Duplicates from Sorted Array (Remove duplicates from sorted array in-place. [Microsoft])
• Container With Most Water (Find container that can store most water. [Amazon])
• Trapping Rain Water (Calculate trapped rainwater. [Amazon])
• Valid Palindrome (Check if string is a palindrome considering only alphanumeric characters. [Facebook])
• Palindrome Number (Check if integer is palindrome without converting to string. [Amazon])
• Minimum Window Substring (Find minimum window containing all characters of another string. [Facebook])
• Longest Palindromic Substring (Find longest palindromic substring. [Amazon])
• Sort Colors (Sort array with values 0, 1, 2 in-place. [Microsoft])
• Merge Sorted Array (Merge two sorted arrays in-place. [Facebook])
• Move Zeroes (Move all zeros to end while maintaining relative order. [Facebook])
• Remove Element (Remove all instances of val in-place. [Amazon])
• Squares of a Sorted Array (Return squares of sorted array in sorted order. [Facebook])
• Backspace String Compare (Compare two strings considering backspaces. [Google])

Sliding Window

• Longest Substring Without Repeating Characters (Find length of longest substring without repeating characters. [Amazon])
• Minimum Window Substring (Find minimum window containing all characters. [Facebook])
• Sliding Window Maximum (Find maximum in each sliding window. [Amazon])
• Longest Substring with At Most Two Distinct Characters (Find longest substring with at most 2 distinct characters. [Google])
• Longest Substring with At Most K Distinct Characters (Find longest substring with at most k distinct characters. [Google])
• Permutation in String (Check if one string contains permutation of another. [Microsoft])
• Find All Anagrams in a String (Find all anagram start indices. [Facebook])
• Longest Repeating Character Replacement (Longest substring with same character after k replacements. [Google])
• Max Consecutive Ones III (Longest subarray with at most k zeros flipped. [Google])
• Fruit Into Baskets (Pick maximum fruits with at most 2 types. [Google])
• Subarrays with K Different Integers (Count subarrays with exactly k distinct integers. [Google])
• Minimum Size Subarray Sum (Find minimum length subarray with sum >= target. [Facebook])

Binary Search

• Binary Search (Search for target in sorted array. [Microsoft])
• Search Insert Position (Find position where target should be inserted. [Amazon])
• First Bad Version (Find first bad version using API calls. [Facebook])
• Search in Rotated Sorted Array (Search in rotated sorted array. [Google])
• Find Minimum in Rotated Sorted Array (Find minimum element in rotated sorted array. [Amazon])
• Search a 2D Matrix (Search in matrix with sorted rows and columns. [Microsoft])
• Kth Smallest Element in a Sorted Matrix (Find kth smallest in sorted matrix. [Google])
• Find Peak Element (Find peak element in array. [Facebook])
• Split Array Largest Sum (Split array into m subarrays to minimize largest sum. [Google])
• Capacity To Ship Packages Within D Days (Find minimum capacity to ship within D days. [Google])
• Koko Eating Bananas (Find minimum eating speed to finish bananas in H hours. [Google])
• Time Based Key-Value Store (Design time-based key-value store. [Google])
• Online Election (Design system to find leader at any time. [Google])
• Random Pick with Weight (Pick index based on weights. [Facebook])

Union Find

• Number of Islands (Count islands in 2D grid. [Facebook])
• Friend Circles (Find number of friend circles. [Google])
• Redundant Connection (Find edge that creates cycle in tree. [Google])
• Accounts Merge (Merge accounts belonging to same person. [Facebook])
• Most Stones Removed with Same Row or Column (Remove maximum stones. [Google])
• Satisfiability of Equality Equations (Check if equality equations are satisfiable. [Google])
• Number of Operations to Make Network Connected (Find operations to connect network. [Microsoft])
• Smallest String With Swaps (Find lexicographically smallest string after swaps. [Amazon])
• Graph Valid Tree (Check if edges form a valid tree. [Facebook])
• Number of Connected Components in Undirected Graph (Count connected components. [Google])

Design Problems

• LRU Cache (Design Least Recently Used cache. [Amazon, Google])
• Design HashMap (Design HashMap without built-in libraries. [Amazon])
• Design HashSet (Design HashSet without built-in libraries. [Facebook])
• Min Stack (Design stack supporting min operation in O(1). [Amazon])
• Implement Queue using Stacks (Design queue using stacks. [Microsoft])
• Implement Stack using Queues (Design stack using queues. [Microsoft])
• Design Twitter (Design simplified Twitter. [Amazon])
• Design Search Autocomplete System (Design autocomplete system. [Google])
• Design Hit Counter (Design hit counter for past 5 minutes. [Google])
• Design Log Storage System (Design log storage and retrieval system. [Google])
• Design In-Memory File System (Design in-memory file system. [Amazon])
• Design Add and Search Words Data Structure (Design data structure supporting add and search. [Facebook])
• Design Word Dictionary (Design dictionary supporting add and search with wildcards. [Facebook])
• LFU Cache (Design Least Frequently Used cache. [Amazon])
• All O(1) Data Structure (Design data structure with all operations in O(1). [Google])
• Insert Delete GetRandom O(1) (Design data structure supporting insert, delete, getRandom in O(1). [Facebook])
• Design Phone Directory (Design phone directory system. [Google])
• Design Tic-Tac-Toe (Design Tic-Tac-Toe game. [Amazon])
• Design Snake Game (Design Snake game. [Amazon])
• Design Chat System (Design basic chat system. [Facebook])
• Design URL Shortener (Design URL shortening service like bit.ly. [Google])