C Online Test

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About the test

The C online test assesses knowledge of programming in the C language through a series of live coding questions.

The assessment includes work-sample tasks such as:

  • Using pointers to reference a location in memory.
  • Implementing and properly using data structures and algorithms.
  • Optimizing memory management and fixing memory leaks.

A good C developer needs a solid understanding of the C programming language and the implications of low-level optimizations to work on complex or performance critical code.

Sample public questions

10 min

Implement the function find_roots to find the roots of the quadratic equation: ax2 + bx + c = 0. The function can assign the roots to the values pointed by root1 and root2 in any order. If the equation has only one solution, the function should assign that solution as both roots. The equation will always have at least one solution.

The roots of the quadratic equation can be found with the following formula: A quadratic equation.

For example, find_roots(2, 10, 8) should assign -1,-4 or -4 and -1 to the values pointed by root1 and root2 as the roots of the equation 2x2 + 10x + 8 = 0 are -1 and -4.

7 min
Data Structure Alignment
Memory Management

Consider the struct UserInfo, which is used in a performance critical sub-system.

Currently, on a system:

  • A long long takes 8 bytes
  • A pointer, a float, and an int take 4 bytes each
  • A short takes 2 bytes
  • A char takes 1 byte

The struct takes 48 bytes of space. Rearrange the struct, without removing, renaming, or changing the type of the members, so that it uses less memory. The code uses pointers to struct members, so struct should be properly aligned.

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23 more premium C questions

Square, Descriptor, Copy Bit, Shipping, Max Sum, Init Range, Increment, Internal Nodes, Battery, Strings Pointer, Allocate String, Count Letters, Segment, Tiles, Read Write Execute, Weighted Average, Node, Racer, Sort Params, Run in Parallel, Chain Link, Paper Strip, Vectors.

Skills and topics tested

  • C
  • Pointers
  • Memory Management
  • Bit Manipulation
  • Arithmetic
  • Algorithmic Thinking
  • Arrays
  • Tree
  • Language
  • Pointer to Pointer
  • Strings
  • 2D Array
  • Pass by Reference
  • Bug Fixing
  • Recursion
  • Multithreading
  • Synchronization
  • Higher Order Function
  • Pthreads
  • Linked List
  • Iteration

For job roles

  • Back-End Developer
  • C Developer

Sample candidate report

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