Quote:How do I solve this C language question?
Advice: First of all, make sure that you understand the requirement.
Then calculate by hand the few first answers of the requirement, say from fun(-1) to fun(10).
Then as you have written the code, check the answers with your hand calculation.
To help you to understand what your code is really doing, there is a tool, its name is Debugger.
Your code do not behave the way you expect, or you don't understand why !
There is an almost universal solution: Run your code on debugger step by step, inspect variables.
The debugger is here to show you what your code is doing and your task is to compare with what it should do.
There is no magic in the debugger, it don't know what your code is supposed to do, it don't find bugs, it just help you to by showing you what is going on. When the code don't do what is expected, you are close to a bug.
To see what your code is doing: Just set a breakpoint and see your code performing, the debugger allow you to execute lines 1 by 1 and to inspect variables as it execute.
Debugger - Wikipedia, the free encyclopedia
Mastering Debugging in Visual Studio 2010 - A Beginner's Guide
Basic Debugging with Visual Studio 2010 - YouTube
1.11 — Debugging your program (stepping and breakpoints) | Learn C++
The debugger is here to only show you what your code is doing and your task is to compare with what it should do.