Midterm (AY22/23)

Problems

3. Integer Division

For two integers a and b, as long as abs(b) is bigger than abs(a), a / b = 0.

6. Redundant Comparisons

Before we talk about this question, let's take a look at what are redundant comparisons from CS1010 Notes:

A condition is redundant if it is always true or always false.

Note that this condition can be part of the logical expression! So, if we can find any part of the logical expression that is always true or false, and if this part is a comparison, then this part will be a redundant comparison

Using this convention, we can easily see that for the option D, the else if condition is always false

// Option D
if (x > y) {
    foo();
} else if (x > y && x == 0)
    bar();
}

For option C, since in the else-if block, we can always say that x <= y, which means x > y is always false, so the condition can be simplified as else if (x == 0).

11. Flowchart*

Whenever you encounter a flowchart that contains the below pattern,

Create a new if block

Create a new if block when converting it into C code!!!

12. Recursion*

Also a very good type of question to test your recursion thinking. Worth to try again.

Note that in this question, the 0 is skipped!!!

Tips

1. Include the essence of the remainder operator % in the cheatsheet!

2. For loop invariant, always remember to check every option in the question! Also remember to include the three requirements for the loop invariants in the cheatsheet.