ITPEC FE Subject B October 2024 Question 3

Array Manipulation — finding the second-largest element by tracking two maximums.

The program maintains two variables: max1 (largest so far) and max2 (second-largest so far), both initialized to -∞.

For each element array[i]:
- Blank A: array[i] > max1 — if the current element exceeds the largest, the old max1 is demoted to max2, and max1 takes the new value.
- Blank B: max2 ← array[i] — if the element doesn't beat max1 but beats max2, it becomes the new second-largest.

Trace with {2, 6, 9, 1, 7, 5}:

Output: max2 = 7 ✓

Why not others:
- (a) array[i] < max1 — entering the "new max" branch when the element is smaller makes no sense
- (b) Same wrong condition as (a), plus B updates max2 instead of promoting correctly
- (c)/(d) array[i] < max2 — triggers on values smaller than the second-max, which is irrelevant
- (e) Correct condition for A, but B sets max1 ← array[i] — max1 is already set on the next line, so this overwrites max2 incorrectly
- (g)/(h) array[i] > max2 — this is the elseif condition, not the primary if condition

Key rule: To find the k-th largest, maintain k tracking variables; when a new maximum is found, cascade the old values down.

AI-generated — may contain errors