C++ Notes

//------------demonstrate I/O---------------
//INPUT: cin or scanf (scanf from <cstudio>)
//OUTPUT: cout or printf (printf from <cstudio>)
/*printf/scanf are from C, while cout/cin are from C++. There's tradeoffs for both,
but printf is usually better for production. */

//---------show common data types-----------
/*
Int ("%d"): 32 Bit integer
Long ("%ld"): 64 bit integer
Char ("%c"): Character type
Float ("%f"): 32 bit real value
Double ("%lf"): 64 bit real value
*/

//----------------random notes---------------
• Vectors vs. C Arrays: C arrays lower-level but fast. vectors allow for easy manipulation at the expense of memory usage.

• map<string, int> m;
  m.insert(make_pair("hello", 17));

• vector<int> v = {1, 2, 3, 4}; //binary search O(logn)
  cout << (binary_search(v.begin(), v.end(), 3) ? : "Found" ? "Not found") << endl;

• vector<int> v = {1, 2, 3, 4};
  auto iter = lower_bound(v.begin(), v.end(), 2); //lower_bound() is O(logn). Returns pointer to val in vector if found, next biggest value if not.
  int index = distance(v.begin(), iter); //upper_bound() is same thing but NOT EQUAL TO only returns first value greater than.
  cout <<



//---------demonstrate templates------------
// inside of numbers.h
template <typename T>
T get_smallest(T num1, T num2)
{
    return num2 < num1? num2 : num1;
}

//----------demonstrate classes----------------
// inside of music.cpp
#include <iostream>
#include "song.h"
int main()
{
    Song my_song("Ignorance", "Paramore");
    std::cout << my_song.get_title() << std::endl;
    return 0;
}

// inside of song.h
#include <string>
class Song {
    private:
        std::string title;
        std::string artist;

    public:
        Song(std::string new_title, std::string new_artist);
        ~Song();
        std::string get_title();
        std::string get_artist();
};

// inside of song.cpp
#include "song.h"
Song::Song(std::string new_title, std::string new_artist)
{
    title = new_title;
    artist = new_artist;
}

Song::~Song()
{
    /* destructors normally aren't needed bc automatically garbage collected when the object moves out of scope, is explicitly deleted, and when the program ends*/
}

std::string Song::get_title() {
    return title;
}

std::string Song::get_artist() {
    return artist;
}

//----------demonstrate references---------------
int a = 23;
int &b = a;
b++;

//----------demonstrate pass-by-reference---------------
void swap_num(int &i, int &j)
{
    int temp = i;
    i = j;
    j = temp;
}

int main()
{
    int a = 100;
    int b = 200;
    swap_num(a, b);
    std::cout << a; //200
    std::cout << b; //100
}

//-----demonstrate pass-by-reference with const-----------
void triple(int const &i)
{
    return i * 3;
}

int main()
{
    std::cout << triple(10) << std::endl; //30
}

//----------demonstrate pointers----------------------
//purpose of a pointer is to share a memory address among other contexts (usually functions).
//& before variable means address of
//* before variable means contents of
int var = 17;
int *pointer = &var;
std::cout << ptr << std::endl; // "0x7fff640295ac"
std::cout << *ptr << std::endl; // dereference operator. "17"
int *pointer; //pointer pointing to... nothing... this is dangerous! Make it "int *pointer = nullptr;" as of C++11.

//--------------demonstrate structs------------------
//combine multiple fields in a single data structure.
//Keep details (name, height, weight) in a single package in the theoretical "Person" class.
struct Student
{
    string first_name;
    string last_name;
    int age;
    double gpa;
};

int main()
{
    Student st;
    st.first_name = "Mika";
    std::cout << st.first_name << std::endl;
    return 0;
}