readme.md

C++ CheatSheet

First Delete all // userinput-- values to get an effective prompt in terminal.

Make sure you have g++ installed, name the file main.cpp and run this

g++ main.cpp -o main.out && ./main.out

c++-cheatsheet.cpp

#include <fstream>
#include <iostream>
#include <string>
#include <vector>

using namespace std;

void learnTypesAndSize() {
    /** TYPES */
    cout << "\n:::: TYPES ::::" << endl;

    const double PI = 3.1415926535;
    char myGrade = 'A';
    bool isHappy = true;
    int myAge = 30;
    float favNum = 3.141592;

    // Other types
    // short int: at least 16 bits
    // long int: at least 32 bits
    // long long int: at least 64 bits
    // unsigned int: same as signed version
    // long double: not less than double

    cout << "Fav number: " << favNum << endl;

    /** SIZE (number of bytes) */
    cout << "\n:::: SIZE ::::" << endl;

    cout << "Size of double: " << sizeof(PI) << endl;
    cout << "Size of char: " << sizeof(myGrade) << endl;
    cout << "Size of bool: " << sizeof(isHappy) << endl;
    cout << "Size of int: " << sizeof(myAge) << endl;
    cout << "Size of float: " << sizeof(favNum) << endl;

    int largestInt = 2147483647;  // cannot be higher
    cout << "Largest integer: " << largestInt << endl;
    largestInt = 2147483648;  // goes out of range
}

void learnMath() {
    /** ARITHMETIC +, -, *, /, %, ++, -- */
    cout << "\n:::: ARITHMETIC ::::" << endl;

    cout << "5 + 2 = " << 5 + 2 << endl;
    cout << "5 - 2 = " << 5 - 2 << endl;
    cout << "5 * 2 = " << 5 * 2 << endl;
    cout << "5 / 2 = " << 5 / 2 << endl;
    cout << "5 % 2 = " << 5 % 2 << endl;

    int five = 5;
    cout << "5++ = " << five++ << endl;  // increment after getting value of five
    cout << "++5 = " << ++five << endl;  // increment before getting value of five
    cout << "5-- = " << five-- << endl;  // decrement after getting value of five
    cout << "--5 = " << --five << endl;  // decrement before getting value of five

    five += 6;  // five becomes 11
    int eleven = five;
    five = 5;  // reassign five
    bool isEqual = eleven == five + 6;
    cout << "isEqual: " << isEqual << endl;  // decrement before getting value of five

    cout << "1 + 2 - 3 * 2 = " << 1 + 2 - 3 * 2 << endl;  // multiplication occurs first
    cout << "(1 + 2 - 3) * 2 = " << (1 + 2 - 3) * 2 << endl;
}

void learnCastType() {
    /** CAST TYPE */
    cout << "\n:::: CAST TYPE ::::" << endl;

    cout << "4 / 5 = " << 4 / 5 << endl;
    cout << "(float)4 / 5 = " << (float)4 / 5 << endl;
}

void learnIf() {
    /** IF STATEMENT */
    cout << "\n:::: IF STATEMENT ::::" << endl;

    int age = 70;
    int ageAtLastExam = 18;
    bool correctVision = true;

    if ((age >= 1) && (age < 16)) {
        cout << "You can't drive" << endl;
    } else if (!correctVision) {
        cout << "Not sure you could drive" << endl;
    } else if (age >= 80 && ((age > 100) || (age - ageAtLastExam) > 5)) {
        cout << "You should pass an exam again" << endl;
    } else {
        cout << "Ok, you can drive" << endl;
    }
}

void learnSwitch() {
    /** SWITCH */
    cout << "\n:::: SWITCH ::::" << endl;

    int greetingOpion = 2;
    switch (greetingOpion) {
        case 1:
            cout << "Bonjour" << endl;
            break;
        case 2:
            cout << "Hola" << endl;
            break;

        default:
            cout << "Hello" << endl;
            break;
    }
}

void learnTernary() {
    /** TERNARY OPERATOR */
    cout << "\n:::: TERNARY OPERATOR ::::" << endl;

    int largestNum = (5 > 2) ? 5 : 2;
    cout << "largestNum :" << largestNum << endl;
}

void learnArray() {
    /** ARRAY */
    cout << "\n:::: ARRAY ::::" << endl;

    int myFavNums[5];
    int badNums[5] = {20, 33, 57, 83, 91};

    cout << "Bad Number 1 :" << badNums[0] << endl;
    char myName[4][5] = {{'A', 's', 't', 'e', 'n'}, {'M', 'i', 'e', 's'}};  // starts with last array definition

    cout << "3rd letter in 2nd array: " << myName[1][2] << endl;  // arrays start at index 0

    myName[1][2] = 'i';                                                     // re-assign new value
    cout << "3rd letter in 2nd array new value: " << myName[1][2] << endl;  // arrays start at index 0
    myName[1][2] = 'e';                                                     // re-assign new value
}

void learnFor() {
    char myName[4][5] = {{'A', 's', 't', 'e', 'n'}, {'M', 'i', 'e', 's'}};

    /** FOR LOOPS */
    cout << "\n:::: FOR LOOPS ::::" << endl;

    for (int i = 1; i <= 10; i++) {
        cout << i << endl;
    }

    for (int j = 0; j < 4; j++) {
        for (int k = 0; k < 5; k++) {
            cout << myName[j][k];
        }

        cout << endl;
    }
}

void learnWhile() {
    /** WHILE LOOPS */  // When you don't know when your loop will end ahead of time
    cout << "\n:::: WHILE LOOPS ::::" << endl;

    int randNum = (rand() % 100) + 1;  // 0 - 99 so we add 1 to reach 100
    while (randNum != 100) {
        cout << randNum << ",";

        randNum = (rand() % 100) + 1;
    }
    cout << endl;

    int index = 1;
    while (index <= 10) {
        cout << index << endl;

        index++;
    }
}

void learnDoWhile() {
    /** DO WHILE LOOPS */  // To execute what is in a while loop at least one time even if the while condition is false
    cout << "\n:::: DO WHILE LOOPS ::::" << endl;

    string numberGuessed;
    int intNumberGuessed = 0;

    do {
        cout << "Guess a number between 1 and 10:  (4 is the answer) ";
        // userinput-- getline(cin, numberGuessed);
        if (numberGuessed.empty()) numberGuessed = "4";

        // stoi converts string to integer, stod converts string to double...
        intNumberGuessed = stoi(numberGuessed);

        cout << intNumberGuessed << endl;

    } while (intNumberGuessed != 4);  // winning number is 4

    cout << "Your win" << endl;
}

void learnString() {
    /** STRING OBJECTS */
    cout << "\n:::: STRING OBJECTS ::::" << endl;

    char happyArray[6] = {'H', 'a', 'p', 'p', 'y', '\0'};  // This is how to create a string in C
    string birthdayString = " Birthday";                   // This is how we create a string in C++
    cout << happyArray + birthdayString << endl;           // Join strings with the concatenation operator

    string yourName;
    cout << "What is your name ? ";
    // userinput-- getline(cin, yourName);  // store user input in yourName, cin is the source input
    if (yourName.empty()) yourName = "Asten Mies";
    cout << "Hello " << yourName << endl;

    double eulersConstant = .57721;
    string eulerGuess;
    double eulerGuessDouble;

    cout << "What is Euler's Constant ? ";
    // userinput-- getline(cin, eulerGuess);
    if (eulerGuess.empty()) eulerGuess = ".55";

    eulerGuessDouble = stod(eulerGuess);
    if (eulerGuessDouble == eulersConstant) {
        cout << "You are right" << endl;
    } else {
        cout << "You are wrong" << endl;
    }

    cout << "Size of string: " << eulerGuess.size() << endl;
    cout << "Is string empty: " << eulerGuess.empty() << endl;
    cout << eulerGuess.append(" was your guess") << endl;

    // compare strings (alphabetical)
    string dogString = "dog";
    string catString = "cat";

    cout << dogString.compare(catString) << endl;  // 1 if it's less than
    cout << dogString.compare(dogString) << endl;  // returns 0 when equal
    cout << catString.compare(dogString) << endl;  // -1 if it's greater than

    string wholeName = yourName.assign(yourName);  // assign a new value
    cout << wholeName << endl;
    // https://youtu.be/Rub-JsjMhWY?t=1613

    // substring
    string firstname;
    firstname.assign(wholeName, 0, 5);  // Get whole name from char 0 for length of 5
    cout << "Substring: " << firstname << endl;

    // find substring in string
    int lastNameIndex = wholeName.find("Mies", 0);  // Start searching for that string at index 0
    string lastName;
    lastName.assign(wholeName, lastNameIndex);
    cout << "Find in string: " << lastName << endl;

    // insert in string (index, substring)
    yourName.insert(5, " Bob");
    cout << "Insert in string: " << yourName << endl;

    // delete from string (index, length)
    yourName.erase(6, 4);
    cout << "Erase from string: " << yourName << endl;

    // replace in string (index, length)
    yourName.replace(0, 5, "Bobby");
    cout << "Replace in string: " << yourName << endl;
}

void learnVector() {
    /** VECTOR */  // Same as arrays but size can change
    cout << "\n:::: VECTOR ::::" << endl;

    vector<int> lotteryNumVect(10);
    int lotteryNumArray[5] = {4, 13, 14, 25, 66};

    lotteryNumVect.insert(lotteryNumVect.begin(), lotteryNumArray,
                          lotteryNumArray + 3);  // (from begin, array to insert, length of the part we want to insert)
    cout << "Insert in vector: " << lotteryNumVect.at(2) << endl;

    lotteryNumVect.insert(lotteryNumVect.begin() + 5, 44);         // starts at index 5
    cout << "Insert in vector: " << lotteryNumVect.at(5) << endl;  // outputs the one that we just inserted at index 5

    lotteryNumVect.push_back(64);  // push from the back
    cout << "First value in vector: " << lotteryNumVect.front() << endl;
    cout << "Final value in vector: " << lotteryNumVect.back() << endl;
    cout << "Vector size: " << lotteryNumVect.size() << endl;
}

/** SEE FUNCTIONS CHAPTER */
int addNumbers(int firstNum, int secondNum = 0) {
    int combinedValue = firstNum + secondNum;
    return combinedValue;
}

// We can overload a function (already defined but re-defining)
int addNumbers(int firstNum, int secondNum, int thirdNum) {
    int combinedValue = firstNum + secondNum + thirdNum;
    return combinedValue;
}

int getFactorial(int number) {
    int sum;
    if (number == 1)
        sum = 1;
    else
        sum = getFactorial(number - 1) * number;

    return sum;
}

void learnFunction() {
    /** FUNCTIONS */
    cout << "\n:::: FUNCTIONS (see top of file) ::::" << endl;

    cout << "Call function addNumbers: " << addNumbers(1) << endl;
    cout << "Call function addNumbers: " << addNumbers(1, 5, 6) << endl;
    cout << "Call function getFactorial of 3: " << getFactorial(3) << endl;
}

int learnFile() {
    /** FILES */
    cout << "\n:::: FILES (read and write) ::::" << endl;

    string steveQuote = "A day without sunshine is like, you know, night";
    ofstream writer("stevequote.txt");

    if (!writer) {
        cout << "Error opening file" << endl;
        return -1;
    } else {
        writer << steveQuote << endl;  // create file was successful? Write into it
    }

    ofstream writer2("stevequote.txt", ios::app);  // append to then end of file
    // ios::binary : Treat the file as binary
    // ios::in : Open a file to read input
    // ios::truc : Default
    // ios::out : Open a file to write output

    if (!writer2) {
        cout << "Error opening file" << endl;
        return -1;
    } else {
        writer2 << "\n - Steve Martin" << endl;  // create file was successful? Write into it
    }

    char letter;  // will hold each character
    ifstream reader("stevequote.txt");

    if (!reader) {
        cout << "Error opening file" << endl;
        return -1;
    } else {  // stream is open

        // Read each character from the stream until the end of the file
        for (int i = 0; !reader.eof(); i++) {
            reader.get(letter);
            cout << letter;
        }

        cout << endl;
        reader.close();
    }
}

void learnException() {
    /** EXCEPTION HANDLING */
    cout << "\n:::: EXCEPTION HANDLING ::::" << endl;

    // division by 0 error
    int number = 0;
    //  Instead of causing an error, with a try block we can catch it and throw a message
    try {
        if (number != 0) {
            cout << 2 / number << endl;
        } else
            throw(number);  // throw is looking for a catch.
    } catch (int number) {
        cout << number << " is not valid" << endl;
    }
}

/** SEE POINTERS CHAPTER */
void makeMeYoung(int* age) {
    cout << "I used to be " << *age << endl;
    *age = 21;
}

void actYourAge(int& age) { age = 42; }

void learnPointer() {
    /** POINTERS */  // Memory addresses
    cout << "\n:::: POINTERS ::::" << endl;

    int myAge = 30;
    char myGrade2 = 'A';

    cout << "Size of int: " << sizeof(myAge) << endl;   // 4 bytes
    cout << "Size of char: " << sizeof(myAge) << endl;  // 1 byte

    // reference this box / memory address with the reference operator &
    cout << "myAge is located at " << &myAge << endl;  // outputs the memory address example: 0x7ffccc557780
                                                       // if we don't use pointers or we don't use reference operators
                                                       // and we change the value of a variable in a function
                                                       // that change of value does not carry on - it is lost

    int* agePtr = &myAge;  // pass that memory address over to our pointer
    cout << "Address of pointer: " << agePtr << endl;
    cout << "Data at memory address: " << *agePtr << endl;  // de-reference to get the data at that memory address

    int badNums2[5] = {20, 33, 57, 83, 91};
    int* numArrayPtr = badNums2;  // create a pointer

    cout << "Address " << numArrayPtr << " Value " << *numArrayPtr << endl;
    numArrayPtr++;  // goes one integer further, so 4 bytes more in the address
    cout << "Next Address " << numArrayPtr << " Value " << *numArrayPtr << endl;

    // PASSING BY POINTER
    // Use pointer when you don't want to initialize at declaration
    // means I can (re-)initialize later
    makeMeYoung(&myAge);  // modify the value through a function
    cout << "I'm " << myAge << " years old now" << endl;

    int& ageRef = myAge;
    cout << "myAge: " << myAge << endl;
    ageRef++;
    cout << "myAge: " << myAge << endl;

    // PASSING BY REFERENCE
    // When ok to initialize at declaration
    // not able to change whatever you're pointing at after that
    actYourAge(ageRef);
    cout << "myAge: " << myAge << endl;
}

/** SEE CLASS CHAPTER */
class Animal {
    // Attributes : height weight modeled in variable
    // Capabilities : Run Eat modeled in methods

   private:  // can only be changed by functions inside this class - called encapsulation
    int height;
    int weight;
    string name;

    static int numOfAnimals;  // is going to be shared by every object of type animal that is going to be created

   public:  // to be able to access the private values - we encapsulate them to keep them protected
    int getHeight() { return height; }
    int getWeight() { return weight; }
    string getName() { return name; }

    // protect the values that are going to be stored
    void setHeight(int cm) { height = cm; };
    void setWeight(int kg) { weight = kg; };
    void setName(string animalName) { name = animalName; };

    // we declare a prototype of a function
    void setAll(int, int, string);

    // a constructor - handle creating every object
    Animal(int, int, string);

    // a destructor
    ~Animal();

    // overloading - a constructor that doesn't receive anything. Should have no arguments
    Animal();

    // static method
    static int getNumberOfAnimals() { return numOfAnimals; };

    void toString();
};

// declare our static
int Animal::numOfAnimals = 0;

void Animal::setAll(int height, int weight, string name) {
    // no animals created yet
    this->height = height;
    this->weight = weight;
    this->name = name;
    Animal::numOfAnimals++;
}

// constructor
Animal::Animal(int height, int weight, string name) {
    this->height = height;
    this->weight = weight;
    this->name = name;
    Animal::numOfAnimals++;
}

Animal::~Animal() { cout << "Animal " << this->name << " destroyed" << endl; }

Animal::Animal() { Animal::numOfAnimals++; }

void Animal::toString() {
    cout << this->name << " is " << this->height << " cms tall and " << this->weight << " kgs in weight " << endl;
}

void learnClass() {
    /** CLASS */
    cout << "\n:::: CLASS ::::" << endl;

    Animal fred;

    fred.setHeight(33);
    fred.setWeight(10);
    fred.setName("Fred");

    cout << fred.getName() << " is " << fred.getHeight() << " cms tall and " << fred.getWeight() << " kgs in weight "
         << endl;

    Animal tom(12, 1, "Tom");
    cout << tom.getName() << " is " << tom.getHeight() << " cms tall and " << tom.getWeight() << " kgs in weight "
         << endl;
}

int main() {
    cout << "Hello" << endl;

    learnTypesAndSize();

    learnMath();

    learnCastType();

    /** COMPARISON OPERATORS: ==, !=, >, <, >=, <= */

    /** LOGICAL OPERATORS: && || ! */

    learnIf();

    learnSwitch();

    learnTernary();

    learnArray();

    learnFor();

    learnWhile();

    learnDoWhile();

    learnString();

    learnVector();

    learnFunction();

    learnFile();

    learnException();

    learnPointer();

    learnClass();

    return 0;
}