Minimum Number of Operations to Make Word K-Periodic
A medium-tier problem at 60% community acceptance, tagged with Hash Table, String, Counting. Reported in interviews at Turing and 0 others.
Minimum Number of Operations to Make Word K-Periodic is a medium-difficulty string problem that hinges on pattern recognition and counting. You're given a word and a period value k, and you need to find the minimum character changes to make the word repeat with that fixed period. Turing has asked it. The acceptance rate sits around 60%, which sounds friendly until you realize most candidates miss the counting optimization on first pass. This is exactly the kind of problem where the brute-force reflex costs you 10 minutes and a wrong answer. If you hit this live and freeze on the grouping strategy, StealthCoder surfaces a working solution invisible to the proctor.
Companies that ask "Minimum Number of Operations to Make Word K-Periodic"
Minimum Number of Operations to Make Word K-Periodic is the kind of problem that decides whether you pass. StealthCoder reads the problem on screen and surfaces a working solution in under 2 seconds. Invisible to screen share. The proctor sees nothing. Made for the engineer who has done the work but might still blank with a webcam pointed at him.
Get StealthCoderThe trick is recognizing that you're not optimizing character changes globally. Instead, you partition the string into k buckets based on position modulo k, then for each bucket, count character frequencies and pick the most common character as the target. The total operations equals the sum of characters you remove from each bucket to make it uniform. Hash table counting is your core tool here. The pitfall is trying to solve it greedily across the whole string or overthinking the period constraint. Most people see 'k-periodic' and imagine sliding windows when you actually need a static partition and frequency count. The acceptance rate suggests plenty of candidates get stuck on the counting logic or waste time on unnecessary iteration. When the assessment is live and the timer is running, StealthCoder runs invisibly and hands you the partition-then-count pattern in seconds, skipping the dead-end attempts that drain your confidence.
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Minimum Number of Operations to Make Word K-Periodic recycles across companies for a reason. It's medium-tier, and most candidates blank under the timer. StealthCoder is the hedge: an AI overlay invisible during screen share. It reads the problem and surfaces a working solution in under 2 seconds. Made for the engineer who has done the work but might still blank with a webcam pointed at him. Works on HackerRank, CodeSignal, CoderPad, and Karat.
Minimum Number of Operations to Make Word K-Periodic interview FAQ
What does 'k-periodic' mean in this problem?+
A word is k-periodic if characters repeat in a fixed cycle of length k. For example, if k=3, character at position 0 must match positions 3, 6, 9, etc. You partition all positions by their remainder when divided by k, then make each group uniform.
How do I count operations efficiently?+
Use a hash table to count character frequencies within each position group (modulo k). For each group, the answer is group size minus the highest frequency. Sum all groups. This avoids nested loops and keeps you linear in string length.
Is this problem actually asked at live interviews?+
Yes. Turing has reported asking it. Medium difficulty with ~60% acceptance means it's screening for solid string handling and pattern decomposition skills. It's real enough that you should understand the modulo partitioning trick before your assessment.
What's the most common mistake candidates make?+
Trying to greedily pick a single character for the entire string or using a sliding window approach. The problem requires you to treat each k-spaced position group independently, count within each group, and sum the results. Misreading this costs you the whole solution.
Do I need advanced algorithms for this?+
No. Hash table and counting are the only tools you need. No dynamic programming, no complex data structures. The challenge is recognizing the partition pattern and coding it cleanly without off-by-one errors or redundant iteration.
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