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Section 7.1 Worked Example: While Loops - Counter

Subgoals for Evaluating a Loop.

  1. Identify loop parts
    1. Determine start condition
    2. Determine update condition
    3. Determine termination condition
    4. Determine body that is repeated
  2. Trace the loop
    1. For every iteration of loop, write down values

Subsection 7.1.1

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Problem: Given the following code, what is the output?
int counter = 0;
int total = 0;

while (counter < 50)
{
    if (counter % 5 == 0)
            total += counter;
    counter++;
 }

 System.out.println(total);

Subsection 7.1.2 SG1: Diagram which statements go together.

Figure 7.1.1.

Subsection 7.1.3 SG2: Define and initialize variables

Start:
counter = 0;
total = 0;
End:
counter >= 50
Figure 7.1.2.

Subsection 7.1.4 SG3: Trace the loop

Figure 7.1.3.
System.out.println(total);
Figure 7.1.4.
  1. For every iteration of loop, write down values
Counter increments by 1, but the value is only added to total when it is evenly divisible by 5.
Figure 7.1.5.
Figure 7.1.6.
Answer.
Output is 225

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