Ransom Note
A easy-tier problem at 65% community acceptance, tagged with Hash Table, String, Counting. Reported in interviews at Disney and 4 others.
Ransom Note is an easy problem that shows up in live OAs at Disney, Microsoft, Spotify, and other major companies. It tests whether you can quickly count character frequencies and compare them, but the trick isn't the algorithm, it's picking the right data structure and avoiding the off-by-one errors that trip people up under time pressure. With a 64% acceptance rate, candidates are failing this not because it's hard, but because they overthink it or implement sloppily. If you hit this problem live and blank on the optimal approach, StealthCoder surfaces a clean, working solution in seconds.
Companies that ask "Ransom Note"
Ransom Note 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 problem asks: can you build a ransom note from letters in a magazine. The obvious trap is trying to match letter by letter. The actual solution is frequency counting, hash the magazine's characters, then decrement as you consume them for the note. Most people reach for a HashMap or array, but the execution matters: you need to handle the case where the note demands more of a letter than the magazine has. The second-order gotcha is handling uppercase, lowercase, and special characters correctly. Many candidates code this in 3-4 minutes but introduce an off-by-one or forget to validate counts before using them. If you're solid on Hash Table basics and String iteration, you'll land this. If you're shaky on loop bounds or HashMap API, StealthCoder removes the risk of a careless miss on a live assessment.
Pattern tags
You know the problem.
Make sure you actually pass it.
Ransom Note recycles across companies for a reason. It's easy-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.
Ransom Note interview FAQ
Is Ransom Note really asked at top companies?+
Yes. Disney, Microsoft, Spotify, Criteo, and Karat all report asking it. It's used to filter for basic data structure fluency without needing advanced tricks. At 64% acceptance, many candidates pass, but a surprising number fail due to sloppy implementation, not lack of understanding.
What's the trick to solving this efficiently?+
Hash the magazine's character counts into a HashMap or frequency array. Then iterate the ransom note and decrement counts. If any character count goes negative or is missing, return false. It's O(m+n) time, O(1) space if you use a fixed-size character array instead of a HashMap.
What mistakes do people make on this problem?+
Forgetting to check that a character exists in the magazine before decrementing. Off-by-one errors in loop bounds. Confusing the order (hashing the note instead of the magazine). Not handling the edge case where the note is longer than the magazine or uses characters the magazine doesn't have.
Is this considered a 'real' interview problem or a warmup?+
It's a warmup. Companies use it early to verify you can code without syntax errors and think clearly under pressure. Passing it quickly builds confidence. Failing it hurts because it signals carelessness, not lack of ability. That's why the problem matters more than its difficulty.
How does Ransom Note relate to the Hash Table and Counting topics?+
It's a direct application. You build a frequency count (Counting), store it in a Hash Table, and validate constraints by iterating the input string again. If you're weak on hash-based counting, this is a template you'll use in harder problems like Group Anagrams or Find All Anagrams in a String.
Want the actual problem statement? View "Ransom Note" on LeetCode →