Minimum Number of K Consecutive Bit Flips
A hard-tier problem at 62% community acceptance, tagged with Array, Bit Manipulation, Queue. Reported in interviews at thoughtspot and 0 others.
Minimum Number of K Consecutive Bit Flips is a hard problem that looks simple until you realize the greedy trap. You're given a binary array and need to find the minimum flips of K consecutive bits to make all ones. ThoughtSpot has asked this. The acceptance rate sits at 62%, which means a third of strong candidates miss the greedy insight or implement it wrong. The trick isn't simulation, it's recognizing that a greedy left-to-right pass works, but tracking which flips affect your current position requires either a queue or a prefix sum trick. If this problem hits your live OA and you blank on the pattern, StealthCoder solves it in seconds, invisible to the proctor.
Companies that ask "Minimum Number of K Consecutive Bit Flips"
Minimum Number of K Consecutive Bit Flips 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 by an Amazon engineer who watched the leaked-problem repo become an industry secret. He decided you should have it too.
Get StealthCoderThe naive approach simulates each flip, but that's O(n*k) and gets rejected. The real solution: scan left to right, and whenever you hit a zero, you must flip it (greedy, flip as early as possible). Track how many active flips affect your current position using a queue of flip start indices or a running count. You need to know whether position i has been flipped an even or odd number of times by flips that started before it. A sliding window tracks flips that are still in effect. Common pitfall: forgetting to validate that you can actually perform a flip at the end, if you need a flip but don't have k bits left, return -1. The topics, Array, Bit Manipulation, Sliding Window, Prefix Sum, all converge here. It's not hard because the code is long; it's hard because the state tracking is easy to botch. StealthCoder is the hedge for the one pattern you didn't drill.
Pattern tags
You know the problem.
Make sure you actually pass it.
Minimum Number of K Consecutive Bit Flips recycles across companies for a reason. It's hard-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 by an Amazon engineer who watched the leaked-problem repo become an industry secret. He decided you should have it too. Works on HackerRank, CodeSignal, CoderPad, and Karat.
Minimum Number of K Consecutive Bit Flips interview FAQ
Why is the greedy approach (always flip immediately when you see a zero) correct?+
A zero at position i must eventually be flipped. Flipping it sooner never makes things worse, and flipping it later only delays progress. If you wait to flip a zero, you're using a flip slot that could've been used on a later problem zero. Greedy left-to-right is optimal.
How do I track which flips affect my current position without simulating the whole array?+
Use a queue of flip start indices. When you process position i, remove flips from the queue that ended before i (flips starting at j with length k affect up to j+k-1). Current position i is flipped if the queue size is odd. This is the sliding window piece.
What happens if I reach the end but still need to flip and don't have k bits left?+
Return -1. You can't make all ones if a zero appears within the last k-1 positions and hasn't been flipped yet. This is the validation check most candidates forget.
Is this really asked at companies like ThoughtSpot, or is it just a hard-problem filter?+
It's in ThoughtSpot's reported problem set. At 62% acceptance, it's not as rare as some hard problems. It filters for people who understand greedy plus state tracking, which matters in real systems.
How does Bit Manipulation relate to this problem if it's mostly array and sliding window?+
The array holds bits (0 and 1), and you're toggling them. Some solutions use XOR or bitmasks to track flip parity. The core algorithm doesn't require bit tricks, but they can simplify the state-tracking logic in implementation.
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