ITPEC FE Subject B October 2024 Question 16

Hamming Distance (extended) — fill in blanks for a function that computes Hamming distance between two strings of possibly different lengths.

The function compares characters up to the shorter string's length, then adds the length difference as extra mismatches.

• •Blank A: `length2 < length1` — minLength starts as length1; overwrite it with length2 only when length2 is smaller (standard min-finding pattern).
• •Blank B: `is not equal to` — Hamming distance counts differing positions, so increment distance when characters do not match.
• •Blank C: `distance + remainingLength` — after the loop, distance holds mismatches in the overlapping part; remainingLength (|length1 - length2|) accounts for extra unmatched characters.

Verification with example:
hammingDistance("101010", "111000111"):
- minLength = 6, differences at positions 2 and 5 → distance = 2
- remainingLength = 9 - 6 = 3
- Result: 2 + 3 = 5 ✓

Why not others:
- (a) remainingLength alone ignores mismatches in the overlapping part
- (b) uses is equal to, which counts matches instead of differences
- (c) distance + minLength adds the overlap length instead of the extra length — wrong value
- (e, f) length2 > length1 flips the condition — minLength would become the max, causing index-out-of-bounds
- (g, h) same flipped condition as (e, f)

Key rule: Hamming distance = mismatches in overlapping portion + length difference for the extra characters.

AI-generated — may contain errors