Self-test 3:
Control flow (Loops)

What will be printed by the following code segment?
```
int i = 9;

while (i >= 0)
{
    cout << i << " ";
    i = i-1;
}
```
Solution

9 8 7 6 5 4 3 2 1 0
What will be printed by the following code segment?
```
int i = 0;

while (i < 10)
{
    cout << 9-i << " ";
    i = i+1;
}
```
Solution

9 8 7 6 5 4 3 2 1 0

What will be printed by the following code segment?

int i = 9;

while (i >= 0)
{
    cout << i << " ";
    i = i-1;
    cout << i << " ";
    i = i-1;
}

Solution

9 8 7 6 5 4 3 2 1 0

What will be printed by the following program?
```
int N = 100;
int i = 0;
int count = 0;

while (i < N)
{
    if (i%2 == 0)
    {
        count = count+1;
    }
}
cout << count << endl;
```
Solution

Nothing! The program will enter into an infinite loop because no codes modify i inside the while-loop. As a result, i will keep its value of zero forever and the while-loop condition is always true.
What is printed by the following program?
```
int i = 0;
int j = 0;

while (i < 3)
{
    while (j < 3)
    {
        cout << j << " ";
        j = j+1;
    }

    cout << endl;
    i = i+1;
}
```
1. ```
0 1 2
0 1 2
0 1 2
```
2. ```
0 1 2
3 4 5
6 7 8
```
3. ```
0 1 2
```
Solution

C.
When the outer while-loop executes for the first time, the inner while-loop executes 3 times. Hence, 3 numbers are printed. After that, j remains at the value of 3. So during the execution of the 2nd and 3rd times of the outer while-loop , the inner while-loop is not executed and only two newlines are printed.
Can the following code segment be compiled and executed? Can the code segment escape from the infinite loop? What will be the final results of a and b after getting out of the while loop?
```
int a = 100;
int b = 200;

while (true)
{
    if (a >= b)
        continue;

    a = a+1;
    b = b-1;
}
```
Solution

It can be compiled and executed without errors but it will end up in an infinite loop because the continue-statement will only go back to check the statement containing the boolean expression of the nearest loop, in this case, the statement: while (true).

Write C++ codes to print the following pattern?

*******
 ***** 
  ***  
   *

Solution

Solution 1:

cout << "*******" << endl;
cout << " ***** " << endl;
cout << "  ***  " << endl;
cout << "   *   " << endl;

Alternative Solution:

    for (int row = 0; row < 4; ++row)
    {
        // Output leading space
        for (int j = 0; j < row; ++j)
            cout << ' ';
        
        // Output leading space
        for (int j = 0; j < 2*(4-row)-1; ++j)
            cout << '*';
        
        cout << endl;
    }

Write a program to print the checker pattern with varying size.

e.g. given:
int SIZE = 4;

0 1 0 1
1 0 1 0
0 1 0 1
1 0 1 0

e.g. given:
int SIZE = 5;

0 1 0 1 0
1 0 1 0 1
0 1 0 1 0
1 0 1 0 1
0 1 0 1 0

Solution

int SIZE = 4;
int row = 0;
int col = 0;

while (row < SIZE)
{
    col = 0;
    while (col < SIZE)
    {
        cout << (row+col)%2 << " ";
        col = col+1;
    }

    cout << endl;
    row = row+1;
}

What is the output of the above program when the user input is 5?

#include <iostream>
using namespace std;

int main(void)
{
    int i = 0, j;
    int number;
    cin >> number;
    i = number;

    while (i > 0)
    {
        j = 0;
        while (j < number-i)
        {
            cout << " ";
            j = j+1;
        }

        j = 0;
        while (j < i)
        {
            cout << "*";
            j = j+1;   
        }

        cout << endl;
        i = i-1;
    }
}

```
*****
 ****
  ***
   **
    *
```
```
*
**
***
****
*****
```
```
*****
***
*
```
```
*****
****
***
**
*
```

Solution

What is printed by the following program?

int num = 3474;
int sum = 0;

while (num > 0)
{
    sum = sum + num%10;
    num = num / 10;
}

cout << sum << endl;

Solution

18. Variable sum is the sum of all individual digits of variable num.

Self-test 3: Control flow (Loops)

Self-test 3:
Control flow (Loops)