5.15. Coding PracticeΒΆ
Q1
Question
Write a program that prints out a 5x5 triangle using asterisks. An example is shown below. Your code should use while loops.
*
**
***
****
*****
1#include <iostream>
2
3int main() {
4 // Write your implementation here.
5}
Answer
Below is one way to implement the program. We use nested loops
similar to the last version of the multiples_table function
to print out the triangular shape.
1#include <iostream>
2using std::cout;
3
4int main() {
5 int row = 0;
6 while (row < 5) {
7 int col = 0;
8 while (col <= row) {
9 cout << '*';
10 col++;
11 }
12 cout << '\n';
13 row++;
14 }
15}
Q2
Encapsulate the triangle printing program into a function called
print_triangle. Generalize it so that it takes a parameter
int n to generate a nxn triangle. Call your function in main
with an input of 4, which should result in the following output:
*
**
***
****
1#include <iostream>
2
3void print_triangle (int n) {
4 // Write your implementation here.
5}
6
7int main() {
8 // Write your implementation here.
9}
Q3
Question
Write a function called print_pyramid that prints out an nx``n`` pyramid using asterisks.
An example is shown below with n equal to 5. Your code should use while loops.
*
***
*****
*******
*********
1#include <iostream>
2
3void print_pyramid (int n) {
4 // Write your implementation here.
5}
6
7int main() {
8 print_pyramid (5);
9}
Answer
Below is one way to implement the program. We use multiple while
loops to print out spaces and asterisks. The outer loop creates the
number of rows, and within the outer loop, the two inner loops
print out the correct number of spaces and asterisks.
1#include <iostream>
2using std::cout;
3
4void print_pyramid(int n) {
5 int count = 1;
6 while (count <= n) {
7 int space = n - count;
8 while (space > 0) {
9 cout << ' ';
10 space--;
11 }
12 int num_asterisks = 2 * count - 1;
13 while (num_asterisks > 0) {
14 cout << '*';
15 num_asterisks--;
16 }
17 cout << '\n';
18 count++;
19 }
20}
21
22int main() {
23 print_pyramid (5);
24}
Q4
Write a function called number_pyramid that prints out an n x n number pyramid.
An example is shown below with n equal to 5. Your code should use while loops.
(Hint: similar to the previous question, if you want the output to look nice, using conditionals
that print different amounts of spaces.)
1
222
33333
4444444
555555555
1#include <iostream>
2
3void number_pyramid (int n) {
4 // Write your implementation here.
5}
6
7int main() {
8 number_pyramid (5);
9}
Q5
Question
A common coding interview question that's also a popular children's game used to teach division is fizz_buzz. Write a program that uses a while loop and prints the numbers 1 through 100, but every multiple of 3 is replaced with the word "Fizz," every multiple of 5 is replaced with the word "Buzz," and every multiple of both 3 and 5 is replaced with "fizz_buzz." Your output should be the following:
1
2
Fizz
4
Buzz
...
14
fizz_buzz
16
...
98
Fizz
Buzz
1#include <iostream>
2
3int main() {
4 // Write your implementation here.
5}
Answer
Below is one way to implement the "fizz_buzz" program. We use conditionals with modulus operators in a while loop to categorize every number and print the correct output. Feel free to search up on the fizz_buzz coding interview problem if you are interested in other ways to code this program!
1#include <iostream>
2
3int main() {
4 using std::cout;
5 int n = 1;
6 while (n <= 100) {
7 if (n % 15 == 0) {
8 cout << "fizz_buzz\n";
9 }
10 else if (n % 3 == 0) {
11 cout << "Fizz\n";
12 }
13 else if (n % 5 == 0) {
14 cout << "Buzz\n";
15 }
16 else {
17 cout << n << '\n';
18 }
19 n++;
20 }
21}
Q6
Write the function addition_table which takes an int n as a parameter
and prints out a nxn addition table. Call your function in main with
"10" as the argument. Your output should look like this:
0 1 2 3 4 5 6 7 8 9 10
1 2 3 4 5 6 7 8 9 10 11
2 3 4 5 6 7 8 9 10 11 12
3 4 5 6 7 8 9 10 11 12 13
4 5 6 7 8 9 10 11 12 13 14
5 6 7 8 9 10 11 12 13 14 15
6 7 8 9 10 11 12 13 14 15 16
7 8 9 10 11 12 13 14 15 16 17
8 9 10 11 12 13 14 15 16 17 18
9 10 11 12 13 14 15 16 17 18 19
10 11 12 13 14 15 16 17 18 19 20
1#include <iostream>
2
3void addition_table (int n) {
4 // Write your implementation here.
5}
6
7int main() {
8 // Call your function here.
9}
Q7
Question
A number is a prime number if its only factors are 1 and itself.
Write the function is_prime, which takes an int num as a parameters.
is_prime is a boolean function that returns true if num is a prime
number and returns false otherwise. Run and test your code!
1bool is_prime (int num) {
2 // Write your implementation here.
3}
Answer
Below is one way to implement the is_prime function. First,
we check to see if num is less than or equal to 1, and return
false if that is the case. Next, we use a while loop
to continuously check if a factor n divides num evenly.
If it does, we return false. If no value of n divides num
evenly, then we return true. Notice the while loop only goes up to
num / 2 because if 2 doesn't divide evenly, then there isn't a smaller factor.
1#include <iostream>
2
3bool is_prime (int num) {
4 if (num <= 1) {
5 return false;
6 }
7 int n = 2;
8 while (n < num / 2) {
9 if (num % n == 0) {
10 return false;
11 }
12 n++;
13 }
14 return true;
15}
Q8
Write a program that uses a while loop to print out the alphabet from 'a' to 'z'.
1#include <iostream>
2
3int main() {
4 // Write your implementation here.
5}
Q9
Question
The Fibonacci sequence is a sequence of numbers such that each successive number is the sum of the two previous numbers. This sequence is as follows: 0, 1, 1, 2, 3, 5, 8, 13, 21, 34, and so on. Write a program that prints the first 20 Fibonacci numbers.
1#include <iostream>
2
3int main() {
4 // Write your implementation here.
5}
Answer
Below is one way to implement the program. First,
we initialize the first two Fibonacci numbers and print the
first two values out right away.
Next we use a while loop to compute the remaining values.
The next number in the sequence is the sum of the previous two,
so we compute the sum and then we need to update the values
of the "previous two Fibonacci numbers" for the next loop iteration.
1 #include <iostream>
2
3 int main() {
4 int first = 0;
5 int second = 1;
6 std::cout << first << ' '
7 << second << ' ';
8 int n = 2;
9 while (n < 20) {
10 int next = first + second;
11 std::cout << next << ' ';
12 first = second;
13 second = next;
14 ++n;
15 }
16 }
Q10
Write a function called factorial which takes an int n as a parameter
and returns n factorial. Remembers that a factorial (denoted by !) is the product of all
positive integers less than or equal to n, so 4! is 24. Use a while loop.
Run and test your code!
1#include <iostream>
2
3int factorial (int n) {
4 // Write your implementation here.
5}