What this is: These pages contain a collection of C puzzles and solutions. The puzzles are short exercises that stress the common building blocks that go into larger programs. Their purpose is to supplement a C textbook and to provide a way to quickly review and reinforce what you already know. These pages are not enough, in themselves, to teach the language.
To learn any subject, you need to practice it. To learn C, you need to write dozens of short programs so that the syntax rules and common strategies become second nature.
The language: The language used for these puzzles is ANSI C. Any ANSI C environment will work. Notepad++ and gcc from the command line work well. All C++ compilers compile ANSI C.
On-line C environments can be used. Here is one that works well with these puzzles: tutorialspoint.
How to use the puzzles: Start at the beginning and solve them one-by-one in order. The puzzles start out easy and gradually become more difficult. Try to work each puzzle. If you merely read the puzzle and then look at the answer you are not using your time effectively.
Don't rush through these. Do a few puzzles, and then stop. Later in the day, or the next day, when ever you have some time available, do a few more. Short practice sessions are more effective than long ones.
Improve Things: Often students stop as soon as their program sort-of works. But their program could be improved, and is just not professional grade. As with other subjects, you can learn more by revising and improving your work.
Break Things: If you have a working program, find ways in which it could fail, and then fix the problems. Look for dangerous assumptions that you have made (such as assuming that integers are always positive, or that a buffer is big enough, or that an array will always contain data.) Some of the suggested solutions may have such problems. Try to find them.
Console Applications: All of these puzzles are "console applications" which means that standard input is from the keyboard and that standard output is to the monitor (on Windows machines, the "DOS Window", sometimes called the "command prompt window").
When a console application runs from within some integrated development environments
the system sends standard
output to a new monitor window it creates.
But when the program stops running,
the window vanishes and you can't see what the program did.
To prevent this, put
Difficulty is rated Easy, Medium, and Hard.
A puzzle rated
These puzzles involve simple expressions. Start Here.
Puzzles E01 - E21
These puzzles involve simple loops.
Puzzles L01 - L10
Puzzles L11 - L20
Puzzles L21 - L30
Puzzles L31 - L40
These puzzles involve using random numbers. Random numbers are surprisingly important in programming. Many of the puzzles in the following sections use random numbers.
Puzzles R01 - R15
These puzzles involve arrays.
Puzzles D01 - D10
Puzzles D11 - D20
Puzzles D21 - D30
Puzzles D31 - D40
Puzzles D41 - D50
These puzzles involve two dimensional arrays. Two dimensional arrays are much less common than one dimensional arrays, but they can be useful.
Puzzles DD01 - DD10
Puzzles DD11 - DD17
These puzzles involve scoping rules.
Puzzles SL01 - SL10 - Block Scope
Puzzles SL11 - SL20 - File Scope
Puzzles SL21 - SL30 - Linkage
Puzzles SL31 - SL40 - Static
Puzzles SL41 - SL50 - More Static
These puzzles involve pointers.
Puzzles P01 - P10
Puzzles P11 - P20
Puzzles P21 - P30
This section is about null terminated strings. You might wish to work this section after going through section P on pointers.
Puzzles S01 - S10
Puzzles S11 - S20
How programs can accept parameters entered as part of the command line.
Command Line Parameters
These puzzles involve structs.
Puzzles T01 - T10
Puzzles T11 - T20
Puzzles T21 - T30
Main Tutorial Menu
C Puzzles is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License.