C Programming Questions

Programming challenges for beginners and mid-level C programmers.

• Arrays
• Strings
• Structures and Unions
• Bit Manipulations
• Pointers
• Memory Management
• Linked Lists
• Stacks and Queues
• Searching
• Sorting
• Linux Internals

Arrays

Easy

• Find the Max-Min in an Unsorted Array
• Find the Missing Number in a 1 to 500 Sequence
• Count Occurrences in a Sorted Array
• Detect Duplicate Numbers
• Rearrange Positive and Negative Numbers
• Move Zeros to the Left
• Rotate an Array Right
• Check for Divisible Sum Pairs
• Locate Target Sum Pairs

Medium

• Remove Duplicate Without Libraries
• Identify Multiple Duplicates
• Find Array Leaders
• Find the Equilibrium Index
• Identify a Peak Element
• Identify the Majority Element
• Merge Sorted Arrays
• Calculate Array Intersection
• Retrieve k-th Max-Min Element
• Find the Minimum Sum Subarray
• Detect a Zero-Sum Subarray
• Calculate the Product of an Array Except Self

Hard

• Locate the Longest Consecutive Subsequence
• Transform a Self-Referential Array
• Implement Quicksort on an Array

Strings

Easy

• Validate if a String is a Palindrome
• Reverse a String Recursively
• Count Character Occurrences in a String
• Count Vowels and Consonants in a String
• Verify a Pangram
• Verify That a String Contains Only Numeric Characters
• Check if Two Strings Are Anagrams
• Find the First Unique Character in a String
• Identify Duplicate Characters in a String
• List Multiple Occurrences of Characters in a String

Medium

• Encode a String Alphabetically
• Convert a String to an Integer Without Built-In Functions
• Reverse Words in a Sentence Without Libraries
• Count Substring Occurrences in a String
• Count Balanced Zero-One Substrings
• Validate Balanced Parentheses in a String
• Verify String Rotations
• Find the Lexicographically Minimal String Rotation
• Identify the Longest Substring Without Repeats
• Evaluate Repeated Substring Patterns

Hard

• Find the Longest Palindromic Substring
• Minimize Palindromic Partitions
• Evaluate String Interleaving
• Generate All String Permutations

Structures and Unions

Easy

• Calculate Student Average Marks
• Manage Employee Addresses
• Calculate a Book Price Discount
• Calculate the Distance between 3D Points
• Perform Time Operations Using Structures
• Perform Complex Number Operations
• Convert Color Systems (RGB to CMYK) Using Unions
• Represent Error Codes Using Unions
• Read File Attributes Into a Structure

Medium

• Implement a Library Database System
• Implement a Vehicle Extended Structure Using Unions
• Implement a Student Linked List
• Parse Commands
• Create a Variable Data Type Array Using Unions
• Calculate Data Differences
• Implement Menu Items with Function Pointers in a Structure
• Identify Network Packet Types Using Unions

Hard

• Access a 32-Bit Value Using a Union
• Convert a 4-Byte Value Using a Union
• Convert an IP Address Using Structures and Unions
• Represent an IP Address Using a Union
• Perform Endianness Conversion Using a Union
• Configure Device Settings Using Bitfields
• Optimize Structure Memory Padding
• Serialize a Data Packet

Bit Manipulations

Easy

• Convert Decimal to Binary
• Count Set Bits
• Detect Power of Two
• Determine if Two Integers Have Opposite Signs
• Find the Parity of a Number
• Isolate the Rightmost Set Bit
• Toggle the 3rd and 5th Bits
• Mask Certain Bits
• Extract n Bits
• Clear Bits from MSB to i

Medium

• Find the Single Number in an Array
• Find a Unique Number in an Array
• Reverse Bits in a Byte
• Rotate Bits
• Swap Odd and Even Bits
• Check for Alternate Bits
• Check if a Number is a Multiple of 3
• Count the Number of Flips to Convert A to B
• Implement Bitwise Right Shift
• Calculate a to the Power of b Using Bit Manipulation
• Implement XOR without using the XOR operator
• Set Bits Without Using Arithmetic Operations

Hard

• Find Two Unique Numbers in an Array
• Check if the Binary Representation of a Number is a Palindrome
• Generate All Possible Combinations of n Bits

Pointers

Easy

• Convert a String to Lowercase
• Trim String Whitespace
• Check if a String is a Palindrome
• Check String Prefix
• Swap Two Strings Using Pointers
• Move a 2D Point
• Calculate the Dot Product of Vectors
• Find Data Type Size Without Using sizeof

Medium

• Concatenate Strings Without a Library
• Split a String into Halves
• Find the First Non-Repeated Character
• Count Array Elements Without a Loop
• Rotate an Array by 'k' Elements
• Segregate Even and Odd Numbers Using Pointers
• Merge Two Sorted Arrays
• Find Array Intersection
• Find Common Elements in Sorted Arrays
• Find Overlapping Elements in Arrays
• Flatten a 2D Array to 1D
• Find the Length of a Linked List
• Check if Pointers Point to the Same Array

Hard

• Implement a Custom memcpy Function
• Implement a Custom strtok Function
• Detect a Pointer Out of Bounds
• Detect Memory Leaks

Memory Management

Easy

• Implement a Custom strdup Function
• Implement a Dynamic Array
• Calculate a Memory Offset
• Check Memory Alignment
• Initialize a Memory Library
• Log Memory Accesses

Medium

• Detect Memory Leaks
• Analyze the Memory Footprint
• Report Memory Statistics
• Detect a Stack Overflow
• Implement a Memory Pool
• Implement a Stack-Based Memory Allocator
• Simulate Write-Once Memory
• Serialize an Object
• Inspect Heap Metadata
• Detect Memory Fragmentation

Hard

• Defragment Memory
• Implement a Memory-Mapped Circular Buffer
• Implement a Memory-Bound Priority Queue
• Manage Memory Overlay
• Implement a Segmented Memory Allocator
• Implement a Slab Allocator
• Simulate Virtual Memory
• Simulate a Garbage Collector
• Check Memory Safety

Linked Lists

Easy

• Find the Length of a Linked List
• Find the Middle Element
• Reverse a Linked List
• Reverse a Linked List (No Recursion)
• Find the n-th Node from the End
• Move the Last Element to the Front
• Delete Alternate Nodes
• Pairwise Swap Elements

Medium

• Detect a Cycle in a Linked List
• Merge Two Sorted Lists
• Remove Duplicates (Unsorted List)
• Remove Nodes of a Specific Value
• Convert a Binary Number to an Integer
• Segregate Even and Odd Nodes
• Compare Strings as Linked Lists
• Find the Intersection Point of Two Lists
• Detect and Remove a Loop
• Check if a Linked List is a Palindrome
• Partition a Linked List Around a Value

Hard

• Add Numbers Represented by Lists
• Implement Merge Sort on a Linked List
• Clone a Linked List with a Random Pointer
• Flatten a Multi-level Linked List
• Find the Common Ancestor in a Binary Tree Using a Doubly Linked List

Stacks and Queues

Easy

• Check for Balanced Parentheses Using a Stack
• Check if a String is a Palindrome Using a Stack
• Implement a Circular Queue
• Implement a Stack with a Get-Min Operation
• Count Nested Statements Using a Stack
• Implement a Queue-Based Logger

Medium

• Implement a Stack-Based Calculator
• Validate Expressions Using a Stack
• Implement a Multi-Stack Array
• Parse Commands Using a Stack or Queue
• Implement a Queue-Based Cache
• Generate Sequences Using a Queue
• Filter Text Using a Queue
• Implement a Priority Queue Using a Heap
• Implement a Queue Supporting Two Priorities
• Implement a String Message Queue
• Implement Undo and Redo Using Stack
• Log Function Calls Using a Stack

Hard

• Implement a Queue Using Stacks
• Sort a Stack
• Perform Post-Order Traversal Using a Stack
• Convert a Recursive Function to Iterative Using a Stack
• Implement a Stack-Based Text Editor
• Implement a Byte-Packing Stack
• Implement Radix Sort Using a Queue

Searching

Easy

• Search Sorted Array
• Search Unsorted Array
• Perform a Recusrive Binary Search
• Perform a Sentinel Search
• Perform a Jump Search
• Count Occurrences of a Number
• Find the First and Last Occurrences
• Find Two Numbers That Sum to 'N'

Medium

• Search an Unknown-Length Array
• Find a Fixed Point
• Find a Peak Element
• Count Array Rotations
• Perform an Interpolation Search
• Perform an Exponential Search
• Perform a Ternary Search
• Find the Missing Number from '1' to 'n'
• Find the Majority Element
• Search a Nearly Sorted Array

Hard

• Search a Sorted Rotated Array
• Perform a Fibonacci Search
• Find the Repeating and Missing Numbers
• Find the Smallest Missing Numbers
• Find the 'k'-th Max-Min Element
• Search a Bitonic Array
• Search a Sorted Matrix

Sorting

Easy

• Implement Optimized Bubble Sort
• Implement Gnome Sort
• Implement Cocktail Sort
• Implement Odd Even Sort
• Implement Comb Sort
• Implement Sleep Sort
• Implement Bogo Sort
• Implement Stooge Sort

Medium

• Implement Cycle Sort
• Implement Pancake Sort
• Implement Pigeonhole Sort
• Implement Counting Sort for Negative Numbers
• Implement Bucket Sort
• Implement Dynamic Gap Shell Sort
• Sort a Linked List Using Insertion Sort
• Implement Bead Sort
• Implement Iterative Quick Sort
• Implement Recursive Merge Sort
• Implement In-Place Merge Sort
• Implement Heap Sort with a Binary Max Heap

Hard

• Implement Radix Sort for Floating-Point Numbers
• Implement Bitonic Sort
• Implement Patience Sort
• Implement Permutation Sort
• Implement Tim Sort

Linux Internals

Easy

• Parse Command-Line Argument
• Copy a File
• Fetch CPU Information
• Traverse a Filesystem Using opendir and readdir
• Implement the chmod Command
• Read a File in User-Space
• Implement the tail Command

Medium

• Implement a Custom ps Command
• Implement Custom malloc and free
• Fork and Wait for Processs
• Create and Synchronize Threads
• Access a File Using Mutexes
• Implement a Simple Shell
• Handle Signals with a Custom Handler
• Implement the ping Command
• Implement the whois Command
• Implement the watch Command
• Implement a CPU Scheduling Algorithm

Hard

• Solve the Producer-Consumer Using Semaphores
• Demonstrate the Priority Inversion Problem
• Implement Priority Inversion Handling
• Create a Custom Init Process
• Communicate Between User-Space and Kernel-Space
• Perform a Zero-Copy Data Transfer
• Implement a Terminal Multiplexer