---
# System prepended metadata

title: BE A CODER (C/CPP track)

---

# BE A CODER (C/CPP track)

## videos

<iframe width="560" height="315" src="https://www.youtube.com/embed/msiXme3fDwk" title="YouTube video player" frameborder="0" allow="accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture" allowfullscreen></iframe>

<iframe width="560" height="315" src="https://www.youtube.com/embed/PEYN3isSyPo" title="YouTube video player" frameborder="0" allow="accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture" allowfullscreen></iframe>

<iframe width="560" height="315" src="https://www.youtube.com/embed/bY2bTXKnHRs?si=UFmfrXOu1NzIaPOx" title="YouTube video player" frameborder="0" allow="accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture; web-share" referrerpolicy="strict-origin-when-cross-origin" allowfullscreen></iframe>

<iframe width="560" height="315" src="https://www.youtube.com/embed/MNYSSQ88Va0" title="YouTube video player" frameborder="0" allow="accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture" allowfullscreen></iframe>

<iframe width="560" height="315" src="https://www.youtube.com/embed/VOHvdoYsvHw" title="YouTube video player" frameborder="0" allow="accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture" allowfullscreen></iframe>

<iframe width="560" height="315" src="https://www.youtube.com/embed/k9GzHxQTD-g" title="YouTube video player" frameborder="0" allow="accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture" allowfullscreen></iframe>

## prior skill (recommand)

- [typing training](https://typethealphabet.app/) complete in 3 secs
- [markdown learning](https://markdown.tw/)

## tools, environments

### mobaxterm [download](https://mobaxterm.mobatek.net)
your shell tool, what is [shell](https://zh.wikipedia.org/zh-tw/殼層)?

### commands in the shell
- ls, touch, cd, cat, mv, rm
- vim
  the editor in CLI(command line interface)
  what is GUI?
- tmux
  a terminal multiplexer
- ~~xdg-open (you can alias to open)
  `alias open='xdg-open'`~~
  use open directly in mobaXterm
- gcc, g++
  your [GNU](https://zh.m.wikipedia.org/zh-tw/GNU) c/c++ compiler
- man, `--help`(`-h`) flag for any command
  how to use the commands?
  
here is a [cygwin introduction](https://nobodyzxc.github.io/2017/05/30/basic-linux/#more), most of the commands are available in mobaxterm, and the rest ones also have corresponding ones in mobaxterm.

and here are some vim intros
- [manipulation](https://nobodyzxc.github.io/2017/01/22/vim-0/#more)
- [configuration](https://nobodyzxc.github.io/2020/11/18/vim-1/#more)

## what is a program



| program | article |
| -------- | -------- |
| Programming Language     | Nature Language    |
| function | paragraph |
| statement; (c/c++) | sentence. |
| expression | word |
| operand / operator | letter |
| order machine | for human mind |

## start from a c/c++ program

```c
#include <stdio.h>
int main(int argc, char **argv){
    puts("hello world");
    return 0;
}
```
### [Flow of Control](https://www.cs.fsu.edu/~myers/c++/notes/control1.html)

<ul>
<li>
<b>Sequential</b>: default mode. Sequential execution of code statements
(one line after another) -- like following a recipe</li>

<li>
<b>Selection</b>: used for decisions, branching -- choosing between 2 or
more alternative paths.  In C++, these are the types of selection
statements:
 <ul>
 <li><tt>if</tt></li>
 <li><tt>if/else</tt></li>
 <li><tt>switch</tt></li>
 </ul>
</li>
<li>
<b>Repetition</b>: used for looping, i.e. repeating a piece of code
multiple times in a row. In C++, there are three types of loops:
 <ul>
 <li><tt>while</tt></li>
 <li><tt>do/while</tt></li>
 <li><tt>for</tt></li>
 </ul>
</li>
</ul>

```clike
#include<stdio.h>
int main(){
    int i = 0;
    while(i < 10){
        if(i < 5) puts("small");
        else puts("big");
        i += 1;
    }
    return 0;
}
```

### Von Neumann Architecture

#### [Von Neumann Architecture](https://medium.com/linkit-intecs/computer-architecture-models-d163cfefd9c5)

![](https://i.imgur.com/8Z7BDav.png)

#### code is also a kind of data

#### storage level
- register
- memory
- external storage (disk, ...)

bit > 0 or 1
byte = 8bit = 2^8 states
KB = 1024 byte
MB = 1024 KB
GB = ...
TB = ...
PB = ... (2^10)

### compiler & interpreter

#### compiler context

program: you
compiler: translator
machine: worker

you want the worker to do something, but the worker doesn't understand your language, so you make the translator communicate with the worker for you (the translator may write down all your commands and pass it to the worker).

> program that convert code from language to language

#### interpreter context

program: you
interpreter: worker that know your language

you can communicate with the worker directly, but his working skill is not good as previous one (the one doesn't know your language)

> program that execute your code directly




![](https://i.imgur.com/4yOkQiH.png)

![](https://i.imgur.com/JO469dM.png)

![](https://i.imgur.com/UWbVu4P.png)

Note:
HTML and markdown **are not** programming languages,
but you can call them **markup languages**.

## build your program in shell

call compiler directly (gcc/g++)
makefile
alias

---

## part I. basic c
### main function, comment and indent

```c
// here is a comment
int main(){ /* no execute */ return 0; }
```

```c
int main(){
    return 0;
}
```

other types of main:

```c
int main( void )
int main( int argc, char *argv[] )
int main( int argc, char *argv[], char *envp[] )
```

and lagacy: void main

### data types, variable, literal, casting and operators

#### types

- void (imcomplete type, cannot to declare variables)
- char (1 byte)
- short (2 bytes)
- int (4 bytes)
- float (4 bytes)
- double (8 bytes)

*keyword*: `unsigned`, `long`

|Type Name	| 32–bit Size	|64–bit Size|
|---|---|---|
|short	|2 bytes	|2 bytes|
|int	|4 bytes	|4 bytes|
|long	|4 bytes	|8 bytes|
|long long	|8 bytes	|8 bytes|

[reference](https://docs.oracle.com/cd/E19253-01/817-6223/chp-typeopexpr-2/index.html)


#### variable

names start with [a-zA-Z] and _

declare a variable with type

```c
// type variable;
int i;
char ch;
// you can have a initial value
int j = 0;
int i; // dumplicate declaration
```

#### scoping

- global (can be accessed anywhere)
- local
- static (would be mentioned in the future)

#### literal

unsigned: `3u`
unsigned long: `314ul`
char literal: `'a'`
decimal literal: `123`
hex literal: `0xff`
oct literal: `0o34`
string literal: `"abcde"` (array)
float literal: `3.14f`
double literal: `3.14`
long double: `3.14L`

#### casting

```c
int a = 3;
double b = a; // (ok)
b = 4.4;
```

implicit:
```c
a = b; // a == ?
```

explicit:
```c
a = (int)b;
```

#### operators

- `=`
- `+`, `-`, `*`, `/`, `%`
- `==`, `>`, `>=`, `<`, `<=`
- `+=`, `-=`, `*=`, `/=`, `%=`
- `&&`, `||`, `&`, `|`, `++`, `--` ...
- `expr ? expr : expr` (ternary operator)

### function

**keyword**: return

```clike

int global = 0;
// return_type function_name (parameter_type variable...)
int f(int a, int b){
    return a + b;
}

void g(int value){
    global = value;
}

int main(void){
    g(5)
    return f(3 + 4 + global); // return the value
}
```

```bash
gcc -o func func.c
./func
echo $?
```

### expression (non-void)

- literal (1, 2.3, "asdf"), variable (a, i)
- combinations of operator and operands (1 + 2, i++, a += 2)
- function (non-void)

### I/O

```c
#include<stdio.h>
int nth;
scanf("%d", &nth);
// note "&" operator, pass the address
printf("hello %dth world\n", nth);
```

introduction: [link](https://openhome.cc/Gossip/CGossip/PrintfScanf.html)

### header files and basic preprocessing

```c
#include<stdio.h>
```

```c
#define N 100
```

### compilation of multiples file and headers

```c
#ifndef _HEADER_H_
#define _HEADER_H_
...
#endif
```

```c
void f(int x, int y);
```

```bash
gcc -c *.c
gcc -o main *.o
```

### control flow

**keyword**: break, continue
- if, else
```clike
if(expr) statement
else statement // optional
    
if(expr) statement
else if(expr) statement // optional
else statement // optional
    
// one-line statement
statement
// compound statement
{
    statement...
}
// above as stmt
    
// cases:

if(a != b) puts("!=");j
else if(a){ puts("a"); } // if no { ... } ?
else puts("b");

if(i % 2)
    puts("a");
    puts("b");
// how to modify?

int true = 1, false = 0;

if(true) puts("hello");
else if(true) puts("world");

if(true) puts("hello");
if(true) puts("world");

if(true) puts("hello");
else puts("hello");

if(false) puts("hello");
else if(false) puts("hello");

if(true) puts("hello"), puts("world");

int i = (1, 2, 3);
```

- while/do-while
```c
while(expr) stmt

do{ stmt } while(expr);

// convert do-while to while
stmt
while(expr) stmt

// cases
int i = 0;
while(i != 10){
    printf("%d\n", i);
    i += 3;
}
// result?

int j = 0;
do{
    printf("%d\n", j);
    j += 3;
}while(j < 10);
// result?
```
- for
```c
for(expr; expr; expr) stmt

for(init; cond; next) stmt
// convert to while
{
    init;
    while(cond){
        stmt
        next;
    }
}

// cases:
// you can ignore any expr in (...)
for(;;;) puts("yes");

int i = 3, j = 90;
for(i = 0; i < 5; i += 2)
    puts("test");

// in newer version gcc/g++ you can declare in (...)
for(int i = 0; i < 10; i++)
  printf("hello %d\n", i);
 
for(int i = 0, j = 0; i + j < 10; i += 1, j += 2)
  printf("i = %d, j = %d\n", i, j);
```

```clike
for(int i = 0; i < 10; i++){
    if(i == 4) continue;
    printf("%d", i);
}

for(int i = 0; i < 10; i++){
    if(i == 4) break;
    printf("%d", i);
}
```

### statement (void)

in most case,
code ended with `;` and `}` (keyword structure).

`1` => expression
`1;` => statement
`for(;;;){ ; }` => statement

```c
int i = 0;
----------
statement

for(i = 0; i < 10; i++){ printf("%d\n", i); }
    -----  ------  ---   -----------------
    expr   expr    expr  expr
                         ------------------
                         statement
---------------------------------------------
    statement
    
a += 1, a += 1, a += 1;
------  ------  ------
expr    expr    expr
--------------
expr
----------------------
expr
-----------------------
statement
```

### array and string (char array)

![](https://i.imgur.com/zEQTMSX.png)


```c
int a1, a2, a3;
#define SIZE 5
int a[SIZE]; // a[0], a[1], [2];
for(int i = 0; i < SIZE; i++)
    a[i] = i, printf("a[%d] = %d", i, a[i]);
    
for(int i = 0; i < sizeof(a) / sizeof(a[0]); i++)
    printf("a[%d] = %d", i, a[i]);
```

initialize array
```c
int a[10] = {0}; // => ?
int b[10] = {1, 2, 3}; // => ?
```

```c
// determine the size automatically
const int a = 3;
a = 5; // error

int scores[] = {1, 2, 3};
char str[] = "hello";
int s[2][3] = {{1, 2, 3}, {3, 4, 3}};
// size of?
printf("size of scores: %lu\n", sizeof(scores) / sizeof(scores[0]));
printf("size of str: %lu\n", sizeof(str) / sizeof(str[0]));
// iterate them?

// pass to function?
int f(int ss[][3]){
    // ...
}

f(s);
// you can ignore the first dimension
```

```c
int data[3][3];
void init(int d[][3], int row){
    for(int i = 0; i < row; i++)
        for(int j = 0; j < 3; j++)
            d[i][j] = 0;
}

// c99
void init(int row, int col, int d[row][col]){
    for(int i = 0; i < row; i++)
        for(int j = 0; j < col; j++)
            d[i][j] = 0;
}
```

> more ways to pass 2d array: [reference](https://www.geeksforgeeks.org/pass-2d-array-parameter-c/)

we will discuss pass array as pointer in the future

---

## exercise

implementations:

1. print 9x9 table

2. write a function that return first position of positive value, otherwise return -1.

```c
int find_pos(int n, int array[n]);
```

3. find max/min value in the array.
```c
int max(int n, int array[n]);
int min(int n, int array[n]);
```

4. sum all the values in the array.
5. return the average value of the sum.
```c
int sum(int n, int array[n]);
float avg(int n, int array[n]); // note the type
```

### practice on UVa

you can use the [command line tool](https://github.com/arafat-hasan/uva-tool)

### practice on [codewars](https://www.codewars.com/)

[even or odd](https://www.codewars.com/kata/53da3dbb4a5168369a0000fe)
[debug the multiply](https://www.codewars.com/kata/50654ddff44f800200000004/train/c)
[sum of positive](https://www.codewars.com/kata/5715eaedb436cf5606000381)
[return negative](https://www.codewars.com/kata/55685cd7ad70877c23000102)
[reverse string](https://www.codewars.com/kata/5168bb5dfe9a00b126000018)

- kyu 8 x4
- kyu 7 x3
- kyu 6 x2
- kyu 5 x1

---

## part II. advanced c

![](https://i.imgur.com/6rbn5wh.png)
[data in memory](https://courses.engr.illinois.edu/cs225/sp2022/resources/stack-heap/)


### recap the scope

- global
- local
- **static**

```c

int f(){
    static int a = 0;
    // statements
    return a++;
}

int main(){
    printf("%d\n", f());
}
```

### advanced data type

- struct
- enum
- union

```c
struct Person {
    char name[10];
    int age;
};

#include<string.h>
int main(){
    struct Person a = { "hello", 10 };
    printf("%s\n", a.name);
    a.name = "world"; // wrong
    strcpy(a.name, "world");
    a.age += 3;
}
```

> bonus: know the usage of [typedef](https://groangao.pixnet.net/blog/post/24474489)

```c
typedef char[10] Name;
typedef int Age;
typedef struct {
    Name name;
    Age age;
} Person;

int main(){
    Person a = { "hello", 3 };
    Person people[10]; // ten people
    return 0;
}
```

```c
enum Day {
    Sunday, // value = 0
    Monday,
    Tuesday,
    Wednesday,
    Thursday,
    Friday,
    Saturday
};

//...
const int Monday = 1;
// if today == Monday
int main(){
    Day today = Monday;
    printf("%d\n", today);
}
```

```c
union Number {
    int i;
    float f;
    double d;
    long l;
};

int main(){
    Number n;
    n.i = 4;
    printf("%d\n", n.i);
    n.d = 3.14;
    printf("%lfn\n", n.d);
    printf("%d\n", n.i);
}
```

### pointer

![](https://i.imgur.com/nnvvc1U.png)


```c
void f(int array[]){ // same as (int *array)
    
}

void g(int array[][3]){
    // same as (int (*array)[3])
    // != (int *array[3])
}
```
[reference](https://stackoverflow.com/questions/69249996/functions-with-multi-dimensional-arrays-as-formal-parameters
) of convertion from array to pointer when pass to function
```c
void modify(int *ptr, int val){
    *ptr = val;
}

int main(){
    int val = 2;
    int *p = &val;
    int **pp = &p;
    printf("%d == %d\n", *p, val);
    modify(p, 3);
    printf("%d != %d\n", *p, val);
    return 0;
}
```

```c
void f(int *array, int r, int c){
    for(int i = 0; i < r; i++){
        for(int j = 0; j < c; j++)
            printf("%d\n", *(array + i * r + j));
    }
} // pass data[*][*] ?

// array of pointer, different from 2d array
// you **can not** pass
// int array[2][2] for g as g(2, 2, array)
// wrong!!!!
void g(int r, int c, int *array[]){
    for(int i = 0; i < r; i++){
        for(int j = 0; j < c; j++)
            printf("%d\n", *(array[i] + j));
    }
}

int main(){
    int a[3][3];
    f(a, 3, 3);
}

// data[*][*] is *data with size
```

![](https://i.imgur.com/ZyxN4sc.png)


### recursion

```c
int gcd(int a, int b) {
    return b ? gcd(b, a % b) : a;
}
```

exercise: implement fib

```c
int fib(int n){
    // 0 1 1 2 3 5
    if .... return ...;
    else ... return ...;
}
```

### dynamic allocation (malloc/free)

allocate on heap

```c
int *ptr = (int*)malloc(100 * sizeof(int));
free(ptr); // you need free after malloc
```

### define data structure

```c
#include<stdio.h>
#include<stdlib.h>
typedef struct Node {
    int value;
    struct Node *next;
} Node, *Nodeptr;

// (.) -> (.) -> (.) -> NULL

int main(){
    Node *node = (Nodeptr)malloc(sizeof(Node));
    (*node).value = 5;
    // node->value = 5;
    node->next = node;
    Nodeptr cur = node;
    while(cur){
        printf("%d", cur->value); // inf
        cur = cur->next;
    }
    return 0;
}
```

> bonus: how to allocate 2D array?

// node operations

```c
// construct a new node
Node* newNode(int val, Node* next){
    
}

// append tail to tail of list
Node* append(Node *cur, Node *tail){

}

// add a new node to list head
Node* cons(Node *cur ,Node *next){
    
}

// release the list
void *deleteList(){
    
}

```
---

## bonus for c

### function pointer

refernece: [link](https://chenhh.gitbooks.io/parallel_processing/content/cython/function_pointer.html)


### advanced preprocessing

```c
#define add(x, y) ((x) * (y))
// if add(x, y) (x * y)
// add(1+2, 3+4)
// (1+2) * (3+4)
```

---

## part III. basic c++

### type casting

```cpp
double d = 3.14;
int a = int(d); // like a function
auto b = 4; // type inference (cpp)
```

### polymorphism

> function overloading

### namespace

```cpp
namespace lib {
    int x;
}

lib::x = 3;

namespace {
    int y;
}

::y = 4;
```

```cpp
std::cout << "hello world" << std::endl;
```

```cpp
using namespace std;
cout << "hello world" << endl;
```

```c
#include<stdio.h>
#include<cstdio>
```
### c++ flavor I/O, string

```cpp
#include<iostream>
int x, y, z;
cin >> x >> y >> z;
cout << x << 3.14;

std::string str;
// why char a[10];
// a = "asdf"; is not ok but
// str = "asdf" is ok?
// int array[10], *ptr;
// array = ptr; // <= not ok?
```

### object oriented programming

```cpp
class Obj {
    public:
        // bonus: other types of constructor
        Obj(int v){
            val = v;
        }
        // other types of constructor
        void show(){
            std::cout << val << std::endl;
        }
        void set(int v){
            val = v;
        }
    private:
        int val;
    protected:
        // bonus: more about oop, inheritance
}

// bonus: inheritance

int main(){
    Obj obj(3);
    // Obj obj = Obj(3);
    obj.show();
    obj.set(4);
    obj.show();
    return 0;
}
```

### reference

```c
void mod(int *var, int val){
    *var = val;
}

void mod(int &var, int val){
    var = val;
}

int main(){
    int a = 3;
    mod(&a, 4);
    mod(a, 5);
    
    int &b = a;
    b = 7;
}
```

### dynamic allocation (new/delete)

```cpp
int main(){
    Obj *obj = new Obj(3);
    delete obj; // delete after every new
    int *arr = new int[10];
    return 0;
}
```

### template (STL)

```cpp
template <class T>
T add(T a, T b){
    return a + b;
}

int main(){
    add(1, 3);
    add(1.3, 1.5);
}
```

```cpp
#include<vector>
using namespace std;
vector<int> vec;
for(int i = 0; i < 10; i++)
    vec.push_back(i);
    // pop_back, push_front, pop_front
for(auto v: vec)
    cout << v << " ";
```

- vector
- map
- set

more STL: [link](https://nobodyzxc.github.io/2017/10/05/cpp-stl/#more)

### data structure



- linked list
```
. -> . -> .
```
- binary tree
```
    .
   / \
  .   .
 / \ / \
.   ..  .
```
- tree, graph
- bfs, dfs

ADT

- stack
- queue
- map
- set


### algorithm

> discussion about complexity
> sorting algorithm collection
> complexity

---

### other resources
[cp1 syllbas](http://newdoc.nccu.edu.tw/teaschm/1041/schmPrv.jsp-yy=104&smt=1&num=703049&gop=00&s=1&tea=114662.htm)
[cp2 syllbas](http://newdoc.nccu.edu.tw/teaschm/1032/schmPrv.jsp-yy=103&smt=2&num=703050&gop=00&s=1&tea=114662.htm)
[my college lesson material](https://drive.google.com/file/d/1B3rCJE9kE9u07CzkUqF1plXP6WRtcysh/view?usp=sharing)