Stage 3 of 11

Coding problems

A curated sheet of 112 well-known problems in teaching order. Statements are the same in Java and Python; only the starter code changes.

0 / 112 solvedEasy 0/67Medium 0/38Hard 0/7Continue

Basics and maths

0/12

Status	Problem	Difficulty	Asked in
Not started	Count the digits of a number	Easy	Asked in: JPMorgan Chase, TCS
Not started	Reverse the digits of an integer	Easy	Asked in: Capgemini, Infosys, Wipro
Pro+	Swap two numbers without a third variable	Easy	Asked in: Accenture, Capgemini, Infosys +1
Pro+	The first n Fibonacci numbers	Easy	Asked in: Capgemini
Pro+	Check whether a year is a leap year	Easy	Asked in: Infosys
Pro+	Check whether a number is an Armstrong number	Easy	Asked in: Oracle, VMware
Pro+	Add the digits until one digit remains	Easy	Asked in: Zupee
Pro+	Check whether a number is prime	Easy	Asked in: Accenture, Capgemini, TCS
Pro+	Build a star pyramid pattern	Easy	Asked in: Accenture, Capgemini, Cognizant
Pro+	Compute an electricity bill from unit slabs	Easy	Asked in: Wipro
Pro+	List all primes up to n (Sieve of Eratosthenes)	Easy-Medium	Asked in: Accenture, Capgemini, TCS
Pro+	Multiply two numbers without the multiplication operator	Easy-Medium	Asked in: Accenture

About basics and maths

Arrays

0/11

Status	Problem	Difficulty	Asked in
Not started	Find the largest and second largest values	Easy	Asked in: Capgemini, Infosys, Razorpay +2
Not started	Find the missing number	Easy	Asked in: Accenture, Coupa
Pro+	Move all zeros to the end	Easy	Asked in: Amazon, Bloomberg, LinkedIn +3
Pro+	Merge two sorted lists	Easy-Medium	Asked in: Capgemini
Pro+	Rotate a list to the right by k steps	Easy-Medium	Asked in: Adobe, Amazon, Apple +3
Pro+	Find the leaders in a list	Easy-Medium
Pro+	Best time to buy and sell a stock	Easy-Medium	Asked in: Adobe, Amazon, Google +3
Pro+	Find the majority element	Easy-Medium	Asked in: Amazon, Atlassian, D. E. Shaw +3
Pro+	Sort a list of 0s, 1s and 2s in one pass	Medium	Asked in: GreyOrange
Pro+	Maximum subarray sum (Kadane)	Medium	Asked in: Adobe, Amazon, Flipkart +3
Pro+	Find the repeating and the missing number	Medium	Asked in: Amazon, Apple, Bloomberg +3

About arrays

Strings

0/17

Status	Problem	Difficulty	Asked in
Not started	Reverse a string	Easy	Asked in: Accenture, Capgemini, Cognizant +2
Not started	Check whether a string is a palindrome	Easy	Asked in: Accenture, Capgemini, Wipro
Pro+	Count vowels, consonants, digits, spaces and other characters	Easy	Asked in: Capgemini, TCS, Wipro
Pro+	Remove special characters, keep letters and digits	Easy	Asked in: Infosys
Pro+	Remove extra spaces from a sentence	Easy
Pro+	Pad a number with leading zeros	Easy	Asked in: Accenture
Pro+	Remove duplicate characters	Easy	Asked in: Cognizant, Infosys, Wipro
Pro+	Check whether two strings are anagrams	Easy	Asked in: Capgemini
Pro+	Longest common prefix of a list of strings	Easy	Asked in: Google, Microsoft, VMware
Pro+	Count each character	Easy-Medium	Asked in: Capgemini, Infosys, TCS +1
Pro+	Find the duplicate characters and their counts	Easy-Medium	Asked in: Accenture, Capgemini
Pro+	Reverse the words in a sentence	Easy-Medium	Asked in: Capgemini, TCS, Wipro
Pro+	Reverse each word and capitalise its first letter	Easy-Medium
Pro+	Compress a string with run counts (aaabb to a3b2)	Easy-Medium	Asked in: Fivetran, TCS
Pro+	Reverse a string but keep the spaces in place	Medium	Asked in: Infosys, Zupee
Pro+	Extract valid dates from a text	Medium	Asked in: Capgemini, Infosys
Pro+	Add two very large numbers given as strings	Medium	Asked in: PhonePe

About strings

Hashing: counting and lookups

0/13

Status	Problem	Difficulty	Asked in
Not started	Two sum	Easy
Not started	First non-repeating character	Easy	Asked in: Amazon, Flipkart, Goldman Sachs +3
Pro+	Count how often each value occurs	Easy	Asked in: Capgemini, Infosys
Pro+	Find the duplicate values in a list	Easy	Asked in: Accenture, Capgemini, Infosys +1
Pro+	Remove duplicates from a list, keeping the order	Easy	Asked in: Cognizant
Pro+	Check whether all characters are unique	Easy	Asked in: Capgemini
Pro+	Find the characters common to two strings	Easy-Medium	Asked in: Capgemini, Infosys
Pro+	Count how often each word occurs	Easy-Medium	Asked in: Infosys
Pro+	Remove repeated words from a sentence	Easy-Medium	Asked in: Infosys
Pro+	Fewest distinct values after removing k items	Medium	Asked in: Fivetran
Pro+	Longest run of consecutive numbers	Medium	Asked in: Amazon
Pro+	Group anagrams together	Medium	Asked in: Amazon, Goldman Sachs, Google +3
Pro+	Count the subarrays that add up to k	Medium	Asked in: Adobe, Amazon, Apple +3

About hashing: counting and lookups

Sorting

0/6

Status	Problem	Difficulty	Asked in
Not started	Sort the characters of a string	Easy	Asked in: TCS
Not started	Sort a list without a library sort (bubble, selection or insertion)	Easy	Asked in: Capgemini
Pro+	Sort words by how often they occur	Easy-Medium	Asked in: Accenture, Wipro
Pro+	Sort a large list fast (merge sort)	Medium	Asked in: Coupa
Pro+	Merge overlapping intervals	Medium	Asked in: Amazon, Google, Microsoft +2
Pro+	Minimum number of railway platforms	Medium	Asked in: Adobe, Amazon, Atlassian +3

About sorting

Binary search

0/6

Status	Problem	Difficulty	Asked in
Not started	Binary search	Easy	Asked in: JPMorgan Chase, Zupee
Not started	Search insert position	Easy	Asked in: Adobe, Amazon, Apple +3
Pro+	Square root without a library function	Easy-Medium	Asked in: Accolite, Amazon, Flipkart +2
Pro+	First and last position of a value in a sorted list	Medium	Asked in: Amazon, Google, Microsoft
Pro+	Search in a rotated sorted list	Medium	Asked in: Adobe, Amazon, Flipkart +3
Pro+	Smallest truck capacity to ship packages in d days	Medium-Hard	Asked in: Amazon, D. E. Shaw

About binary search

Two pointers and sliding window

0/7

Status	Problem	Difficulty	Asked in
Not started	Pair with a target sum in a sorted list	Easy	Asked in: Adobe, Amazon, Apple +3
Not started	Largest sum of k consecutive values	Easy	Asked in: NPCI, OYO
Pro+	Count pairs whose difference is at most k	Medium	Asked in: Amazon
Pro+	Container with the most water	Medium	Asked in: Amazon, Flipkart, Google
Pro+	Longest substring without repeating characters	Medium	Asked in: Coupa
Pro+	Three numbers that add up to zero (3 sum)	Medium	Asked in: Adobe, Amazon, Flipkart +3
Pro+	Trapping rain water	Hard	Asked in: Adobe, Amazon, Flipkart +3

About two pointers and sliding window

Recursion and backtracking

0/7

Status	Problem	Difficulty	Asked in
Not started	Fast power: x to the power n, modulo 1,000,000,007	Easy-Medium
Not started	All subsets of a list	Medium	Asked in: Adobe, Amazon, Apple +3
Pro+	All permutations of a list	Medium	Asked in: Adobe, Amazon, Apple +3
Pro+	Combination sum: reach a target with reusable values	Medium	Asked in: Adobe, Amazon, Microsoft +1
Pro+	Generate balanced brackets up to a depth limit	Medium
Pro+	Word search in a letter grid	Medium	Asked in: Amazon, Apple, Intuit +2
Pro+	Find all dictionary words in a letter grid	Hard	Asked in: Airbnb, Amazon, Apple +3

About recursion and backtracking

Linked list

0/9

Status	Problem	Difficulty	Asked in
Not started	Reverse a linked list	Easy	Asked in: AMD
Not started	Middle node of a linked list	Easy	Asked in: Adobe, Amazon, Flipkart +3
Pro+	Merge two sorted linked lists	Easy	Asked in: Amazon, Flipkart, Microsoft +3
Pro+	Remove the nth node from the end of a linked list	Easy-Medium	Asked in: Adobe, Amazon, Apple +3
Pro+	Check whether a linked list is a palindrome	Easy-Medium	Asked in: Accolite, Adobe, Amazon +3
Pro+	Detect a loop in a chain of links and find where it starts	Medium	Asked in: Adobe, Amazon, Apple +3
Pro+	Add two numbers stored as linked lists	Medium	Asked in: Adobe, Amazon, Apple +3
Pro+	Insert a value into a sorted circular linked list	Medium-Hard	Asked in: Amazon, Microsoft, Zoho
Pro+	Reverse a linked list in groups of k	Hard	Asked in: Adobe, Amazon, Goldman Sachs +3

About linked list

Stack and queue

0/6

Status	Problem	Difficulty	Asked in
Not started	Balanced brackets	Easy-Medium	Asked in: Swiggy
Not started	Build a queue from two stacks	Easy-Medium	Asked in: Adobe, Amazon, Apple +3
Pro+	Min stack: a stack that knows its smallest value	Medium	Asked in: Adobe, Amazon, Flipkart +3
Pro+	Next greater element for every value	Medium	Asked in: Adobe, Amazon, Flipkart +2
Pro+	Maximum of every window of size k	Hard	Asked in: Adobe, Amazon, Apple +3
Pro+	Largest rectangle in a histogram	Hard	Asked in: Google, Microsoft, NPCI

About stack and queue

Trees

0/10

Status	Problem	Difficulty	Asked in
Not started	Inorder traversal of a binary tree	Easy	Asked in: Deloitte
Not started	Maximum depth (height) of a binary tree	Easy	Asked in: Adobe, Amazon, Apple +3
Pro+	Level order traversal of a binary tree	Easy-Medium	Asked in: Adobe, Amazon, Flipkart +3
Pro+	Check whether two binary trees are the same	Easy	Asked in: Amazon, Flipkart, Microsoft
Pro+	Check whether a binary tree is a mirror of itself	Easy	Asked in: Adobe, Amazon, Apple +3
Pro+	Diameter of a binary tree	Medium	Asked in: Amazon, Microsoft, NPCI +1
Pro+	Insert a value into a binary search tree	Easy-Medium	Asked in: Deloitte
Pro+	Check whether a binary tree is a valid binary search tree	Medium	Asked in: Adobe, Amazon, Flipkart +3
Pro+	Lowest common ancestor of two nodes in a binary tree	Medium	Asked in: Amazon, American Express, Flipkart +3
Pro+	Maximum path sum in a binary tree	Hard	Asked in: Flipkart, Google, Meta +1

About trees

Further problems

0/8

Status	Problem	Difficulty	Asked in
Not started	Climbing stairs: count the ways	Easy	Asked in: Adobe, Amazon, Flipkart +3
Not started	Largest total with no two neighbours (house robber)	Easy-Medium	Asked in: Adobe, Amazon, Flipkart +3
Pro+	Fewest coins or notes to make an amount	Medium	Asked in: Amazon
Pro+	Fewest jumps to reach the end of a list	Medium-Hard	Asked in: Amazon
Pro+	Count the islands in a grid	Medium	Asked in: Amazon, Apple, Google +3
Pro+	Rotting oranges: minutes until every orange is rotten	Medium-Hard	Asked in: Amazon
Pro+	Build a growable list from scratch	Medium	Asked in: Cognizant
Pro+	LRU cache: evict the least recently used entry	Hard	Asked in: Adobe, Amazon, Flipkart +3

About further problems

Not startedIn progressSolvedPro+

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