Minimum Number of Frogs Croaking
A medium-tier problem at 51% community acceptance, tagged with String, Counting. Reported in interviews at Zoox and 1 others.
You're parsing a string that's supposed to represent frogs croaking in sync. The string contains interleaved 'c', 'r', 'o', 'a', 'k' characters, and you need to figure out the minimum number of frogs required to produce that exact sequence. Zoox and Roblox have both asked this. The catch: it's not about counting letters. It's about understanding state machines. A single frog goes through a fixed 4-step cycle (c to r to o to a to k), then it's free to croak again. If you misread this as a simple counting problem, you'll fail test cases. If you blank during the assessment, StealthCoder reads the problem and surfaces the state-tracking solution in seconds, invisible to the proctor.
Companies that ask "Minimum Number of Frogs Croaking"
Minimum Number of Frogs Croaking 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. Built by a senior engineer who knows the OA is theater. This is the script.
Get StealthCoderThe trick is tracking how many frogs are 'in progress' at each step of the croak cycle. Every 'c' starts a croak and increments an in-progress counter. Every 'r' means a frog that was on 'c' moves to 'r'. Same logic flows through 'o', 'a', and 'k'. When you hit 'k', a frog completes its croak and becomes available. The maximum number of frogs in progress at any moment is your answer. Common mistake: treating this as a simple substring-search problem or counting unique letters. That won't work. You need to simulate the state machine and handle invalid sequences (r without prior c, out-of-order transitions). Most candidates see 'string' and 'counting' and jump to character frequency. That's the trap. The actual pattern is constraint-based state tracking. During a live OA, if the examples don't immediately click, you risk running out of time rewriting. StealthCoder removes that risk.
Pattern tags
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Minimum Number of Frogs Croaking 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. Built by a senior engineer who knows the OA is theater. This is the script. Works on HackerRank, CodeSignal, CoderPad, and Karat.
Minimum Number of Frogs Croaking interview FAQ
How do I know if a sequence is even valid?+
Every character must follow the exact cycle c-r-o-a-k in order. If you see 'r' before any 'c', or 'a' before 'o', the sequence is invalid and you return -1. At the end, all frogs must have completed their croak (no frogs stuck mid-cycle). Check this as you iterate.
Is this still being asked at real companies?+
Yes. Zoox and Roblox both have recent reports of this problem. The 50% acceptance rate signals it's a genuine filter in technical interviews, not a warm-up. Expect it if you're interviewing at those companies or similar mid-tier tech shops.
What's the difference between this and a bracket-matching problem?+
Bracket matching tracks depth and pairing. This tracks sequential state transitions. With brackets, you care about nesting. With frogs, you care about the progression through a fixed 5-character sequence. The mental model is different: not 'matching', but 'state machine.'
Can I solve this without tracking individual frogs?+
Yes. Instead of labeling frog objects, track counters for how many frogs are waiting at each state (waiting for r, waiting for o, etc.). Increment the counter when you see that character, decrement when a frog moves to the next state. The maximum counter value across all states is your answer.
Why is the acceptance rate only 50% if it's just counting?+
Because most people treat it as counting. They miss the state-machine constraint, hardcode solutions for simple inputs, or fail on validation edge cases. Once you see the state-tracking pattern, it's straightforward. The 50% rate reflects the trick, not the implementation difficulty.
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