C++ Tutorial

6. Functions

6.1 Void functions

24
1
# include <iostream>
2
# include <string>
3
# include <cmath>
4

5
using namespace std;
6

7
void SayHi(){
8
    cout << "Hello User!";
9
}
10

11
void SaySomething(string name, int age){
12
    cout << "Hello " << name << "! You are " << age << " years old.";
13
}
14

15
int main(){
16
    cout << "Top" << endl;
17
    SayHi(); // the SayHi() function does not return any value, so it cannot be chained with << endl.
18
    cout << endl << "Bottom" << endl;
19

20
    SaySomething("Mike", 35) ;
21

22
    cout << endl;
23
    return 0;
24
}

Result:

4
1
Top
2
Hello User!
3
Bottom
4
Hello Mike! You are 35 years old.

6.2 Return functions

19
1
# include <iostream>
2
# include <string>
3
# include <cmath>
4

5
using namespace std;
6

7
double cube(double num){
8
    double result = num * num * num;
9
    return result;
10
}
11

12
int main(){
13
    double num; 
14
    cout << "Enter a number: ";
15
    cin >> num; 
16
    double answer = cube (num);
17
    cout << answer << endl;
18
    return 0;
19
}

Result:

2
1
Enter a number: 5
2
125

7. If

7.1 If Logical

21
1
# include <iostream>
2
# include <string>
3

4
using namespace std;
5

6
int main(){
7
    bool is_male = false;
8
    bool is_tall = false;
9

10
    if(is_male && is_tall){
11
        cout << "You are a tall male." << endl;
12
    } else if(is_male && !is_tall){
13
        cout << "You are a short male." << endl;
14
    } else if(!is_male && is_tall){
15
        cout << "You are a tall but not male." << endl;
16
    } else if(!is_male && !is_tall){
17
        cout << "You are not tall and not male." << endl;
18
    }
19

20
    return 0;
21
}

Result:

1
1
You are not tall and not male.

7.2 If Comparison

28
1
# include <iostream>
2
# include <string>
3
# include <cmath>
4

5
using namespace std;
6

7

8
int getMax(double num_1, double num_2, double num_3){
9
    
10
    double result;
11

12
    if(num_1 >= num_2 && num_1 >= num_3){
13
        result = num_1;
14
    } else if(num_2 >= num_3 && num_2 >= num_1){
15
        result = num_2;
16
    } else{
17
        result = num_3;
18
    }
19

20
    return result;
21
}
22

23
int main(){
24
    
25
    cout << getMax(2, 5, 8) << endl;
26

27
    return 0;
28
}

Result:

1
1
8

8. A Calculator

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34
1
# include <iostream>
2
# include <string>
3

4
using namespace std;
5

6
int main(){
7
    
8
    double num_1, num_2;
9
    char op;
10

11
    cout << "Enter first number: ";
12
    cin >> num_1;
13
    cout << "Enter operator: ";
14
    cin >> op;
15
    cout << "Enter second number:";
16
    cin >> num_2;
17

18
    double result;
19
    if(op == '+'){
20
        result = num_1 + num_2;
21
    } else if(op == '-'){
22
        result = num_1 - num_2;
23
    } else if(op == '*'){
24
        result = num_1 * num_2;
25
    } else if(op == '/'){
26
        result = num_1 / num_2;
27
    } else {
28
        cout << "Invalid Operator!" << endl;
29
    }
30

31
    cout << result << endl;
32
    
33
    return 0;
34
}

Result:

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4
1
Enter first number: 5
2
Enter operator: *
3
Enter second number:7
4
35

9. Switch

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51
1
# include <iostream>
2
# include <string>
3

4
using namespace std;
5

6
string getDayOfWeek(int day_num){
7

8
    string day_name;
9
    
10
    switch (day_num) {
11
    case 1:
12
        day_name = "Monday";
13
        break;
14
    case 2:
15
        day_name = "Tuesday";
16
        break;
17
    case 3:
18
        day_name = "Wednesday";
19
        break;
20
    case 4:
21
        day_name = "Thursday";
22
        break;
23
    case 5:
24
        day_name = "Friday";
25
        break;
26
    case 6:
27
        day_name = "Saturday";
28
        break;
29
    case 7:
30
        day_name = "Sunday";
31
        break;
32
    default: 
33
        day_name = "Invalid Day Number!";
34
    }
35

36
    return day_name;
37
}
38

39

40
int main(){
41
    
42
    string answer;
43
    int day_num;
44

45
    cout << "Enter a number:";
46
    cin >> day_num;
47
    answer = getDayOfWeek(day_num);
48
    cout << answer << endl;
49
    
50
    return 0;
51
}

Result:

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2
1
Enter a number:4
2
Thursday

10. While Loop

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16
1
# include <iostream>
2
# include <string>
3

4
using namespace std;
5

6
int main(){
7
    
8
    int index = 1;
9
    // index <=5 called while guard statement
10
    while(index <=5){
11
        cout << index << endl;
12
        index++;
13
    }
14
    
15
    return 0;
16
}

Result:

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5
1
1
2
2
3
3
4
4
5
5

10.2 do While Loop

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17
1
# include <iostream>
2
# include <string>
3

4
using namespace std;
5

6

7
int main(){
8
    
9
    int index = 6;
10

11
    do{
12
        cout << index << endl;
13
        index++;
14
    } while(index <=5);
15
    
16
    return 0;
17
}

Result:

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1
1
6

11. Guessing Game

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31
1
# include <iostream>
2
# include <string>
3

4
using namespace std;
5

6

7
int main(){
8
    
9
    int guess;
10
    int guess_count =0;
11
    int guess_limit = 3;
12
    int true_num = 88;
13

14
    while( guess != true_num && guess_count < guess_limit){
15
        cout << "Enter a number: " ;
16
        cin >> guess;
17
        if(guess == true_num){
18
            cout << "You Win!" << endl;
19
        }
20
        if(guess != true_num && guess_count < guess_limit-1){
21
            cout << "Guess again!" << endl;
22
        }
23
        guess_count++;
24
    }
25

26
    if(guess_count == guess_limit && guess != true_num){
27
        cout << "You Lose!" << endl;
28
    }
29
    
30
    return 0;
31
}

Solution:

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32
1
# include <iostream>
2
# include <string>
3

4
using namespace std;
5

6

7
int main(){
8
    
9
    int guess;
10
    int guess_count =0;
11
    int guess_limit = 3;
12
    int true_num = 88;
13
    bool out_of_guess = false;
14

15
    while( guess != true_num && !out_of_guess){
16
        if(guess_count < guess_limit){
17
            cout << "Enter a number: " ;
18
            cin >> guess;
19
            guess_count++;
20
        } else{
21
            out_of_guess = true;
22
        }
23
    }
24

25
    if(out_of_guess){
26
        cout << "You Lose!" << endl;
27
    } else{
28
        cout << "You Win!" << endl;
29
    }
30
    
31
    return 0;
32
}

12. For Loop

12.1 Syntax

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3
1
for (statement 1; statement 2; statement 3) {
2
  // code block to be executed
3
}

Statement 1 is executed (one time) before the execution of the code block.

Statement 2 defines the condition for executing the code block.

Statement 3 is executed (every time) after the code block has been executed.

12.2 Example

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9
1
#include <iostream>
2
using namespace std;
3

4
int main() {
5
  for (int i = 0; i < 5; i++) {
6
    cout << i << "\n";
7
  }
8
  return 0;
9
}

Result:

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5
1
0
2
1
3
2
4
3
5
4

12.3 Example 2

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15
1
# include <iostream>
2
# include <string>
3

4
using namespace std;
5

6
int main(){
7

8
    int nums[] = {1, 2, 3, 4};
9
    
10
    for(int i =0 ; i < 5; i++){
11
        cout << nums[i] << endl;
12
    }
13
    
14
    return 0;
15
}

Result:

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5
1
1
2
2
3
3
4
4
5
78216376

12.3 Example 3

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16
1
# include <iostream>
2
# include <string>
3

4
using namespace std;
5

6

7
int main(){
8

9
    int nums[] = {1, 2, 3, 4, 5};
10
    
11
    for(int i =1 ; i < 6; i++){
12
        cout << nums[i] << endl;
13
    }
14
    
15
    return 0;
16
}

Result:

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5
1
2
2
3
3
4
4
5
5
1

13. Exponent Function

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21
1
# include <iostream>
2
# include <string>
3

4
using namespace std;
5

6

7
int power(int base_num, int pow_num){
8
    int result = 1;
9
    for(int i = 0; i < pow_num; i++){
10
        result = result * base_num;
11
    }
12

13
    return result;
14
}
15

16
int main(){
17

18
    cout << power(2, 3) << endl;
19
    
20
    return 0;
21
}

Result:

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1
1
16

14. 2D Array & Nested Loop

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23
1
# include <iostream>
2
# include <string>
3

4
using namespace std;
5

6

7
int main(){
8

9
    int number_grid[3][2] = {
10
        {1,2},
11
        {3,4},
12
        {5,6}
13
    };
14
    
15
    for(int i = 0; i < 3; i++){
16
        for(int j = 0; j < 2; j++){
17
            cout << number_grid[i][j] << endl;
18
        }
19

20
    }
21

22
    return 0;
23
}

Result:

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6
1
1
2
2
3
3
4
4
5
5
6
6

15. Pointer

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26
1
# include <iostream>
2
# include <string>
3

4
using namespace std;
5

6

7
int main(){
8

9
    int age = 19;
10
    int *pAge = &age;
11
    double gpa = 3.5;
12
    double *pGpa = &gpa;
13
    string name = "Mike";
14
    string *pName = &name;
15

16
    cout << &age << endl;
17
    cout << pAge << endl;
18
    // dereference
19
    cout << *pAge << endl;
20
    cout << *&age << endl;
21

22
    cout << &*pAge << endl;
23
    cout << &*&age << endl;
24

25
    return 0;
26
}

Result:

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6
1
0x16db0f078
2
0x16db0f078
3
19
4
19
5
0x16db0f078
6
0x16db0f078

16. Class

16.1 Object

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31
1
# include <iostream>
2
# include <string>
3

4
using namespace std;
5

6

7
class Book {
8
    public:
9
        string title;
10
        string author;
11
        int pages;
12

13
};
14

15
int main(){
16

17
    Book book_1;
18
    book_1.title = "Harry Potter";
19
    book_1.author = "JK Rowling";
20
    book_1.pages = 500;
21

22
    Book book_2;
23
    book_2.title = "Lord of the Rings";
24
    book_2.author = "Tolkein";
25
    book_2.pages = 700;
26

27
    cout << book_1.author << endl;
28

29
    return 0;
30
}
31

Result:

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1
1
JK Rowling

16.2 Constructor

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40
1
# include <iostream>
2
# include <string>
3

4
using namespace std;
5

6

7
class Book {
8
    public:
9
        string title;
10
        string author;
11
        int pages;
12

13
        Book(){
14
            title = "no title";
15
            author = "no author";
16
            pages = 0;
17
        }
18

19
        Book(string aTitle, string aAuthor, int aPages){
20
            title = aTitle;
21
            author = aAuthor;
22
            pages = aPages;
23
        }
24

25
};
26

27

28
int main(){
29

30
    Book book_0;
31

32
    Book book_1("Harry Potter", "JK Rowling", 500 );
33

34
    Book book_2("Lord of the Rings", "Tolkein", 700 );
35

36
    cout << book_0.author << endl;
37
    cout << book_1.author << endl;
38

39
    return 0;
40
}

Result:

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2
1
no author
2
JK Rowling

16.3 Function

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49
1
# include <iostream>
2
# include <string>
3

4
using namespace std;
5

6

7
class Student {
8
    public:
9
        string name;
10
        string major;
11
        double gpa;
12

13
        Student(){
14
            name = "no title";
15
            major = "no author";
16
            gpa = 0;
17
        }
18
        Student(string aName, string aMajor, double aGpa){
19
            name = aName;
20
            major = aMajor;
21
            gpa = aGpa;
22
        }
23

24
        bool isHonor(){
25
            if(gpa >= 3.5){
26
                return true;
27
            }
28
            return false;
29
        }
30

31
};
32

33

34
int main(){
35

36
    Student student_0;
37

38
    Student student_1("Jim", "Art", 2.4 );
39

40
    Student student_2("Mike", "Business", 3.8 );
41

42
    cout << student_0.name << endl;
43
    cout << student_1.major << endl;
44

45
    cout << student_0.isHonor() << endl;
46
    cout << student_2.isHonor() << endl;
47

48
    return 0;
49
}

Result:

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4
1
no title
2
Art
3
0
4
1

16.4 Getter & Setter

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49
1
# include <iostream>
2
# include <string>
3

4
using namespace std;
5

6

7
class Movie {
8

9
    private:
10
        string rating;
11

12
    public:
13
        string name;
14
        string director;
15
        
16
        Movie(){
17
            name = "no name";
18
            director = "no director";
19
            rating = "no rating";
20
        }
21
        Movie(string aName, string aDirector, string aRating){
22
            name = aName;
23
            director = aDirector;
24
            setRating(aRating);
25
        }
26

27
        void setRating(string aRating){
28
            if(aRating == "G" || aRating == "PG" || aRating == "PG-13" || aRating == "R" || aRating == "NR"){
29
                rating = aRating;
30
            } else {
31
                rating = "NR";
32
            }
33
        }
34

35
        string getRating(){
36
            return rating;
37
        }
38

39
};
40

41
int main(){
42

43
    Movie avangers("The Avengers", "Joss Whedon", "PG-13");
44
    avangers.setRating("adhkjh");
45

46
    cout << avangers.getRating() << endl;
47

48
    return 0;
49
}

Result:

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1
1
NR

16.5 Inheritance

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46
1
# include <iostream>
2
# include <string>
3

4
using namespace std;
5

6

7
class Chef {
8

9
    public:
10
        void makeChicken(){
11
            cout << "The chef makes chicken." << endl;
12
        }
13
        void makeSalas(){
14
            cout << "The chef makes salad." << endl;
15
        }
16
        void makeSpecialDish(){
17
            cout << "The chef makes BBQ beef." << endl;
18
        }
19

20
};
21

22
class ItialianChef : public Chef{
23

24
    public:
25
        void makePasta(){
26
            cout << "The chef makes salad." << endl;
27
        }
28
        // You can over write the function
29
        void makeSpecialDish(){
30
            cout << "The chef makes salad." << endl;
31
        }
32

33
};
34

35
int main(){
36

37
    Chef chef;
38
    chef.makeSpecialDish();
39

40
    ItialianChef itialianChef;
41
    itialianChef.makeSpecialDish();
42
    itialianChef.makeChicken();
43

44

45
    return 0;
46
}

Result:

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3
1
The chef makes BBQ beef.
2
The chef makes salad.
3
The chef makes chicken.