C/C++ Interview Quick Notes
========

# C 語言

## Pointer

### Pointer of variable

- A variable hold the address (一個指向某個儲存位址的變數)

Example:

    int val = 10;
    int * prt = &val

詳細可以參考 Mr. Open Gate 的文章 [C/C++ - 常見 C 語言觀念題目總整理（適合考試和面試）](http://mropengate.blogspot.com/2017/08/cc-c.html)

### Array and Pointer 的關係

在 C 語言中，處理字串一定會牽扯到 char pointer ，在基礎處理上要很注意

- https://www.geeksforgeeks.org/difference-pointer-array-c/
- https://www.geeksforgeeks.org/pointer-vs-array-in-c/

### Function Pointer

- 設計目的：
- can be used to simplify code by providing a simple way to select a function to execute based on run-time values. [Function Pointer, wiki](https://en.wikipedia.org/wiki/Function_pointer)

## 變數範圍 Variable scope 和 生命週期 Variable life time

- 常見有 local, static, global
被宣告為 static 的 variable 有效的生命週期是『只要在程式還在執行都可以使用』，範圍只有在宣告的區域（Ex: function) 才能被存取

詳細可以參考 [Scope and Lifetime of Variables in C](https://blog.feabhas.com/2010/09/scope-and-lifetime-of-variables-in-c/)

## Static function

效果1：當 function 前面加上 static 後，只能在同一個檔案中的 source code 使用 (即是 scope 的概念)
- 類似 OOP (C++) 中的 access modifier，限制 scope 和 EX: private, protect, public

// source code in file1.c
static int sum(int a, int b) ....

// source code in file2.c
sum(10,5) // compiler error

效果2：不同檔案中，被宣告為 static 的 function，因為 scope 只有在該檔案，所以可以在不同檔案中重複使用該 function 的名字，compiler 會認為是不同的 function (會有一點confused要小心一點)

// source code in file1.c
static int sum(int a, int b) ....

// source code in file2.c
static int sum(int a, int b) ....
sum(10,5) // compiler error

[Detail: Static functions in C](https://www.geeksforgeeks.org/what-are-static-functions-in-c/)

解釋：[link1](https://softwareengineering.stackexchange.com/questions/250126/static-vs-non-static-with-non-oop-functions)

## Declaration and Definition 差別

## 記憶體配置 Memory allocation

請參考 Mr. Open Gate 的文章 [C/C++ - 常見 C 語言觀念題目總整理（適合考試和面試）] 的 [用心去感覺] 記憶體的配置

## Struct Memory with Compiler Optimization

<iframe src="//www.slideshare.net/slideshow/embed_code/key/gDVgIO0rg38cDQ?startSlide=203" width="595" height="485" frameborder="0" marginwidth="0" marginheight="0" scrolling="no" style="border:1px solid #CCC; border-width:1px; margin-bottom:5px; max-width: 100%;" allowfullscreen> </iframe> <div style="margin-bottom:5px"> <strong> <a href="//www.slideshare.net/olvemaudal/deep-c" title="Deep C" target="_blank">Deep C</a> </strong> from <strong><a href="//www.slideshare.net/olvemaudal" target="_blank">Olve Maudal</a></strong> </div>

## Source code 如何被 compile 成執行檔

可以參考一下投影片『How A Compiler Works: GNU Toolchain』，至少有概念就好(p9~p14)

<iframe src="//www.slideshare.net/slideshow/embed_code/key/pIAwbkbnVdXxBY" width="595" height="485" frameborder="0" marginwidth="0" marginheight="0" scrolling="no" style="border:1px solid #CCC; border-width:1px; margin-bottom:5px; max-width: 100%;" allowfullscreen> </iframe> <div style="margin-bottom:5px"> <strong> <a href="//www.slideshare.net/jserv/how-a-compiler-works-gnu-toolchain" title="How A Compiler Works: GNU Toolchain" target="_blank">How A Compiler Works: GNU Toolchain</a> </strong> from <strong><a href="https://www.slideshare.net/jserv" target="_blank">Jim Huang</a></strong> </div>

# C++ Object-Oriented Programming

## Encapsulation

Access modifier

- public
- private
- protect: can be access by derived class

## Inheritance

## Polymorphism

- virtual function

[Commonly Asked OOP Interview Questions | Set 1](https://www.geeksforgeeks.org/commonly-asked-oop-interview-questions/)

# Problems
normal swap
swap without temp
review linked-list
static function
difference of tcp and udp
3-way handshape
DHCP
grep
code review
implement strcpy
topology
subnet mask (16 server)
assign value to char* char[]
strlen(*ptr) ok

# Main References

- Interview Problems
- [C/C++ - 常見 C 語言觀念題目總整理（適合考試和面試）](http://mropengate.blogspot.com/2017/08/cc-c.html)
- https://www.geeksforgeeks.org/commonly-asked-c-programming-interview-questions-set-1/
- https://www.geeksforgeeks.org/commonly-asked-c-programming-interview-questions-set-2/

- Reading Material
- [Deep C (and C++), 強烈推薦](https://www.slideshare.net/olvemaudal/deep-c)

- Tutorial Material
- https://www.learn-c.org/
- https://beginnersbook.com/2014/01/c-tutorial-for-beginners-with-examples/