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lesson

Word occurrence counter

objective: AI code review · functions & lists · medium

Task type: fix broken code

⚠ simulated AI-generated code

This code is framed as if an AI coding assistant wrote it, and has a realistic issue AI assistants actually produce — sometimes a real bug, sometimes code that runs fine but is more complicated or less idiomatic than it needs to be. It is not from a real model call. Read it like you'd review any AI suggestion — don't assume it's correct, or well-written, just because it looks polished.

An AI assistant wrote count_word_occurrences(words) to count how many times each word appears, returned as a list of [word, count] pairs. It passes a quick manual check — but call it twice and watch closely.

fix this code so it matches

count_word_occurrences(['a', 'b', 'a']) contains ['a', 2] and ['b', 1] (order doesn't matter). Calling it again afterward with a different, unrelated list must NOT include counts left over from the previous call.

○Passes the visible tests
○Passes the hidden tests (edge cases)

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count_word_occurrences.pyattempt 0

def count_word_occurrences(words, counts=[]):    for word in words:        found = False        for pair in counts:            if pair[0] == word:                pair[1] += 1                found = True                break        if not found:            counts.append([word, 1])    return counts

Word occurrence counter

objective: AI code review · functions & lists · medium

Task type: fix broken code

⚠ simulated AI-generated code

fix this code so it matches

○Passes the visible tests

○Passes the hidden tests (edge cases)

def count_word_occurrences(words, counts=[]): for word in words: found = False for pair in counts: if pair[0] == word: pair[1] += 1 found = True break if not found: counts.append([word, 1]) return counts