1. 기초

1. 네임스페이스

InputOutput

#include <iostream>
using namespace std;

namespace silla {
int year = 935;

void CentralArea() {
    cout << "경상도" << endl;
}
}  // namespace silla

namespace baekjae {
int year = 660;

void CentralArea() {
    cout << "충청도" << endl;
}
}  // namespace baekjae

int main() {
    cout << "신라 중심지: ";
    silla::CentralArea();
    cout << "신라 멸망연도: " << silla::year << endl;

    cout << "백제 중심지: ";
    baekjae::CentralArea();
    cout << "백제 멸망연도: " << baekjae::year << endl;

    return 0;
}

신라 중심지: 경상도
신라 멸망연도: 935
백제 중심지: 충청도
백제 멸망연도: 660

2. `#include`

InputOutput

#include <iostream>
#include <vector>
using namespace std;

int main() {
    vector<int> exam;
    exam.push_back(10);
    exam.push_back(20);
    exam.push_back(30);

    for (int i = 0, size = exam.size(); i < size; i++) {
        cout << "벡터 값: " << exam.at(i) << endl;
    }

    return 0;
}

벡터 값: 10
벡터 값: 20
벡터 값: 30

3. 캐스트 연산자

InputOutput

#include <iostream>
using namespace std;

int main() {
    int x = 2;
    double y = 4.4;

    int i = static_cast<int>(y / x);
    int j = (int)y / x;
    double k = y / x;

    cout << "4.4 / 2 = (static_cast<int>) " << i << endl;
    cout << "4.4 / 2 = (int) " << j << endl;
    cout << "4.4 / 2 = " << k << endl;

    return 0;
}

4.4 / 2 = (static_cast<int>) 2
4.4 / 2 = (int) 2
4.4 / 2 = 2.2

4. 명시적 변환

InputOutput

#include <iostream>
using namespace std;

int main() {
    int number1 = 65;
    double number2 = 23.4;

    int number3 = int(number2);
    double number4 = double(number1 / number2);

    char ch = char(number1);

    cout << "number1: " << number1 << endl;
    cout << "number2: " << number2 << endl;
    cout << "number3: " << number3 << endl;
    cout << "number4: " << number4 << endl;
    cout << "ch: " << ch << endl;

    return 0;
}

number1: 65
number2: 23.4
number3: 23
number4: 2.77778
ch: A

5. 타입 크기

InputOutput

#include <iostream>
using namespace std;

class Temp {
    int no;
    bool is_on;
};

int main() {
    cout << "char 타입 크기: " << sizeof('p') << endl;
    cout << "int 타입 크기: " << sizeof(10) << endl;
    cout << "double 타입 크기: " << sizeof(10.0) << endl;
    cout << "Temp 클래스 크기: " << sizeof(Temp) << endl;

    return 0;
}

char 타입 크기: 1
int 타입 크기: 4
double 타입 크기: 8
Temp 클래스 크기: 8

6. 실수 소수점

InputOutput

#include <cmath>
#include <iostream>
using namespace std;

int main() {
    cout << "== 소수점 버리기 ==" << endl;
    cout << "floor(1.1): " << floor(1.1) << endl;
    cout << "floor(2.3): " << floor(2.3) << endl;
    cout << "floor(-40.5): " << floor(-40.5) << endl;
    cout << "floor(-55.7): " << floor(-55.7) << endl;

    cout << "== 소수점 올리기 ==" << endl;
    cout << "ceil(1.1): " << ceil(1.1) << endl;
    cout << "ceil(2.3): " << ceil(2.3) << endl;
    cout << "ceil(-40.5): " << ceil(-40.5) << endl;
    cout << "ceil(-55.7): " << ceil(-55.7) << endl;

    cout << "== 소수점 반올림하기 ==" << endl;
    cout << "round(1.1): " << round(1.1) << endl;
    cout << "round(2.3): " << round(2.3) << endl;
    cout << "round(-40.5): " << round(-40.5) << endl;
    cout << "round(-55.7): " << round(-55.7) << endl;

    return 0;
}

== 소수점 버리기 ==
floor(1.1): 1
floor(2.3): 2
floor(-40.5): -41
floor(-55.7): -56
== 소수점 올리기 ==
ceil(1.1): 2
ceil(2.3): 3
ceil(-40.5): -40
ceil(-55.7): -55
== 소수점 반올림하기 ==
round(1.1): 1
round(2.3): 2
round(-40.5): -41
round(-55.7): -56

7. 절대값과 제곱수

InputOutput

#include <cmath>
#include <iostream>
using namespace std;

int main() {
    cout << "== 절대값 구하기 ==" << endl;
    cout << "-10의 절대값: " << abs(-10) << endl;
    cout << "-5.72의 절대값: " << fabs(-5.72) << endl;

    cout << "== 제곱수 구하기 ==" << endl;
    cout << "2의 2승: " << pow(2, 2) << endl;
    cout << "3의 4승: " << pow(3, 4) << endl;

    return 0;
}

== 절대값 구하기 ==
-10의 절대값: 10
-5.72의 절대값: 5.72
== 제곱수 구하기 ==
2의 2승: 4
3의 4승: 81

8. 몫과 나머지

InputOutput

#include <iostream>
using namespace std;

int main() {
    double x = 5.7;
    int div1 = static_cast<int>(x / 5);
    double mod1 = x - 5 * static_cast<int>(x / 5);

    int y = 10;
    int div2 = static_cast<int>(y / 2);
    double mod2 = y % 2;

    cout << "5.7 / 5 = 몫: " << div1 << ", 나머지: " << mod1 << endl;
    cout << "10 / 2 = 몫: " << div2 << ", 나머지: " << mod2 << endl;

    return 0;
}

5.7 / 5 = 몫: 1, 나머지: 0.7
10 / 2 = 몫: 5, 나머지: 0

9. 제곱근

InputOutput

#include <cmath>
#include <iostream>
using namespace std;

int main() {
    cout << "4의 제곱근: " << sqrt(4.0) << endl;
    cout << "16의 제곱근: " << sqrt(16) << endl;
    cout << "64의 제곱근: " << sqrt(64) << endl;
    cout << "256의 제곱근: " << sqrt(256.0) << endl;

    return 0;
}

4의 제곱근: 2
16의 제곱근: 4
64의 제곱근: 8
256의 제곱근: 16

10. 소수점 분리

InputOutput

#include <cmath>
#include <iostream>
using namespace std;

int main() {
    double x = 1.2345;
    double div = 0.0;
    double mod = 0.0;

    mod = modf(x, &div);

    cout << "1.2345의 몫: " << div << ", 나머지: " << mod << endl;

    return 0;
}

1.2345의 몫: 1, 나머지: 0.2345

11. 난수 생성

InputOutput

#include <ctime>
#include <iostream>
using namespace std;

int main() {
    srand(static_cast<unsigned int>(time(NULL)));

    for (int i = 0; i < 5; i++) {
        cout << "난수: " << rand() << endl;
    }

    return 0;
}

난수: 1421060440
난수: 1597176793
난수: 204772451
난수: 1341781463
난수: 595271494

12. 날짜와 시간 문자열 변환

InputOutput

#include <ctime>
#include <iostream>
using namespace std;

int main() {
    time_t now = time(NULL);
    tm *ptm = localtime(&now);

    char buffer[100];
    strftime(buffer, 100, "예제 만드는 지금은 %Y년 %m월 %d일, %p %H시 %M분 %s초입니다.\n", ptm);

    cout << buffer;

    return 0;
}

예제 만드는 지금은 2022년 01월 12일, PM 15시 57분 1641970662초입니다.

13. 시간 측정

InputOutput

#include <ctime>
#include <iostream>
using namespace std;

int main() {
    time_t start = time(NULL);
    time_t finish = time(NULL);

    int pass_int = 1;

    time(&start);

    for (int i = 1; i < 100000; i++) {
        for (int j = 1; j < 100000; j++) {
            pass_int += 1;
        }
    }

    time(&finish);

    cout << "1을 100억 번 더하는 시간: "
         << difftime(finish, start) << "초" << endl;

    return 0;
}

1을 100억 번 더하는 시간: 5초

14. 함수 오버로딩

InputOutput

#include <iostream>
using namespace std;

int Plus(int arg1, int arg2) {
    return arg1 + arg2;
}

double Plus(double arg1, double arg2, double arg3) {
    return arg1 + arg2 + arg3;
}

int main() {
    int number1 = Plus(2, 4);
    double number2 = Plus(3.4, 5.7, 8.4);

    cout << "number1: " << number1 << endl;
    cout << "number2: " << number2 << endl;

    return 0;
}

number1: 6
number2: 17.5

15. 디폴트 매개변수

InputOutput

#include <iostream>
using namespace std;

int GetOne() { return 1; }

int Plus(int x, int y = GetOne(), int z = 1) {
    return x + y + z;
}

int main() {
    int number1 = Plus(1);
    int number2 = Plus(1, 2);
    int number3 = Plus(1, 2, 3);

    cout << "결과값: " << number1 << ", "
         << number2 << ", " << number3 << endl;

    return 0;
}

결과값: 3, 4, 6

16. 가변인자 함수

InputOutput

#include <stdarg.h>

#include <iostream>
using namespace std;

int Sum(int args, ...) {
    va_list ap;
    va_start(ap, args);

    int sum = 0;

    for (int i = 0; i < args; i++)
        sum += va_arg(ap, int);

    va_end(ap);

    return sum;
}

int main() {
    int number = Sum(5, 1, 2, 3, 4, 5);

    cout << "1에서 5까지 합: " << number << endl;

    return 0;
}

1에서 5까지 합: 15

17. 인라인 함수

InputOutput

#include <iostream>
using namespace std;

inline int Max(int x, int y) {
    return x > y ? x : y;
}

int main() {
    for (int i = 0; i < 5; i++)
        cout << Max(i, i + 10) << endl;

    return 0;
}

18. `typedef`

InputOutput

#include <iostream>
using namespace std;

typedef enum State {
    OPEN,
    CLOSE,
    DISCONNECT
} state_;

struct Status {
    state_ machine1;
    state_ machine2;
} status_;

int main() {
    status_.machine1 = OPEN;
    status_.machine2 = DISCONNECT;

    cout << "machine1 상태: " << status_.machine1 << endl;
    cout << "machine2 상태: " << status_.machine2 << endl;

    return 0;
}

machine1 상태: 0
machine2 상태: 2

19. `using`

InputOutput

#include <iostream>
#include <vector>
using namespace std;

namespace MyArea {
int Plus(int x, int y) { return x + y; }
}  // namespace MyArea

using namespace MyArea;
using MyVector = vector<int>;

int main() {
    MyVector data = MyVector();
    data.push_back(1);
    data.push_back(2);

    cout << "Data: " << data.at(0) << ", " << data.at(1) << endl;
    cout << "Plus: " << Plus(2, 4) << endl;
}

Data: 1, 2
Plus: 6

20. `auto`

InputOutput

#include <iostream>
#include <string>
using namespace std;

int GetInt() { return 1; }
double GetDouble() { return 1.11; }
string GetString() { return "3"; }

auto add(int x, int y) -> int {
    return x + y;
}

int main() {
    auto data1 = GetInt();
    auto data2 = GetDouble();
    auto data3 = GetString();
    auto data4 = add(5.1, 10.2);

    cout << "Data1: " << data1 << ", "
         << typeid(data1).name() << endl;
    cout << "Data2: " << data2 << ", "
         << typeid(data2).name() << endl;
    cout << "Data3: " << data3 << ", "
         << typeid(data3).name() << endl;
    cout << "Data4: " << data4 << ", "
         << typeid(data4).name() << endl;

    return 0;
}

Data1: 1, i
Data2: 1.11, d
Data3: 3, NSt3__112basic_stringIcNS_11char_traitsIcEENS_9allocatorIcEEEE
Data4: 15, i

21. `decltype`

InputOutput

#include <iostream>
using namespace std;

int main() {
    auto data1 = 1;
    decltype(data1) data2 = 2;
    auto data3 = 3.4;
    decltype(data2 + data3) data4 = 3;

    cout << "Data1: " << data1 << ", "
         << typeid(data1).name() << endl;
    cout << "Data2: " << data2 << ", "
         << typeid(data2).name() << endl;
    cout << "Data3: " << data3 << ", "
         << typeid(data3).name() << endl;
    cout << "Data4: " << data4 << ", "
         << typeid(data4).name() << endl;

    return 0;
}

Data1: 1, i
Data2: 2, i
Data3: 3.4, d
Data4: 3, d

22. `constexpr`

InputOutput

#include <iostream>
using namespace std;

constexpr int GetNumber1() {
    return 2;
}

constexpr int GetNumber2(int x, int y) {
    return x + y;
}

int main() {
    int array1[GetNumber1()];
    int array2[GetNumber2(1, 2)];

    cout << sizeof(array1) << ", "
         << sizeof(array2) << endl;

    return 0;
}

8, 12

23. 람다

InputOutput

#include <iostream>
using namespace std;

auto func1 = []() { cout << "Lambda Function" << endl; };
auto func2 = [](int x, int y) -> bool { return x < y; };

int main() {
    int x = 2;

    auto func3 = [=](int y) {
        func1();
        cout << "x < y = " << func2(x, y) << endl;
    };

    func3(4);

    auto func4 = [=](int y) { return x * x + y * y; };

    cout << "x * x + y * y = " << func4(5) << endl;

    return 0;
}

Lambda Function
x < y = 1
x * x + y * y = 29

24. 실수 `0` 확인

InputOutput

#include <cmath>
#include <iostream>
using namespace std;

int main() {
    double number1 = 1;
    double number2 = 0.4;
    double number3 = 0.0;
    double number4 = 11.2;

    cout << boolalpha;
    cout << isnormal(number1) << endl;
    cout << isnormal(number2) << endl;
    cout << isnormal(number3) << endl;
    cout << isnormal(number4) << endl;

    return 0;
}

true
true
false
true

25. NAN 확인

InputOutput

#include <cmath>
#include <iostream>
using namespace std;

int main() {
    double number1 = 1;
    double number2 = 0.4;
    double number3 = 0.0;
    double number4 = 11.2;

    cout << boolalpha;
    cout << isnan(number1 / number4) << endl;
    cout << isnan(number2 / number3) << endl;
    cout << isnan(number3 / number3) << endl;
    cout << isnan(number4 / number1) << endl;

    return 0;
}

false
false
true
false

26. 좌변과 우변 크기 확인

InputOutput

#include <cmath>
#include <iostream>
using namespace std;

int main() {
    int x = 10;
    int y = 20;
    double a = 12.2;
    double b = 5.6;

    cout << boolalpha;

    cout << "== 좌변 > 우변 ==" << endl;
    cout << isgreater(20, 11) << endl;
    cout << isgreater(x, y) << endl;
    cout << isgreater(a, b) << endl;
    cout << isgreater(x, b) << endl;

    cout << "== 좌변 < 우변 ==" << endl;
    cout << isless(20, 11) << endl;
    cout << isless(x, y) << endl;
    cout << isless(a, b) << endl;
    cout << isless(x, b) << endl;

    return 0;
}

== 좌변 > 우변 ==
true
false
true
true
== 좌변 < 우변 ==
false
true
false
false

27. 두 숫자 차이 확인

InputOutput

#include <cmath>
#include <iostream>
using namespace std;

int main() {
    cout << fdim(-1.0, 0.0) << endl;
    cout << fdim(1.0, 0.0) << endl;
    cout << fdim(0.0, 0.0) << endl;
    cout << fdim(5, 1) << endl;
    cout << fdim(6, 15) << endl;
    cout << fdim(4.9, 1.1) << endl;
    cout << fdim(5.9, 20.1) << endl;

    return 0;
}

1. 기초

1. 네임스페이스

2. #include

3. 캐스트 연산자

4. 명시적 변환

5. 타입 크기

6. 실수 소수점

7. 절대값과 제곱수

8. 몫과 나머지

9. 제곱근

10. 소수점 분리

11. 난수 생성

12. 날짜와 시간 문자열 변환

13. 시간 측정

14. 함수 오버로딩

15. 디폴트 매개변수

16. 가변인자 함수

17. 인라인 함수

18. typedef

19. using

20. auto

21. decltype

22. constexpr

23. 람다

24. 실수 0 확인

25. NAN 확인

26. 좌변과 우변 크기 확인

27. 두 숫자 차이 확인

2. `#include`

18. `typedef`

19. `using`

20. `auto`

21. `decltype`

22. `constexpr`

24. 실수 `0` 확인