String Matching interview questions
22 string matching problems tagged across recent interview reports. Drilled most heavily by autodesk, capital one, and google.
String Matching covers 22 distinct problems that ask you to find, locate, or verify substrings, patterns, or character sequences within larger strings. It's a core pattern at Autodesk, Capital One, Google, and Palantir, where candidates regularly face variants ranging from simple prefix checks to complex multi-pattern searches. The pattern feels straightforward until you hit edge cases: overlapping matches, case sensitivity rules, or the need to optimize beyond brute force. StealthCoder solves these variants in real time when they appear in your live assessment, so you don't freeze on an unfamiliar twist.
Most-asked string matching problems
| # | Problem | Diff | # Companies | Pass % |
|---|---|---|---|---|
| 01 | Find the Index of the First Occurrence in a String | EASY | 19 | 45% |
| 02 | Rotate String | EASY | 7 | 64% |
| 03 | Shortest Palindrome | HARD | 5 | 41% |
| 04 | Count Prefix and Suffix Pairs II | HARD | 4 | 27% |
| 05 | Number of Subarrays That Match a Pattern I | MEDIUM | 4 | 67% |
| 06 | Subtree of Another Tree | EASY | 4 | 50% |
| 07 | Maximum Repeating Substring | EASY | 3 | 40% |
| 08 | String Transformation | HARD | 3 | 25% |
| 09 | Add Bold Tag in String | MEDIUM | 2 | 51% |
| 10 | Check If a Word Occurs As a Prefix of Any Word in a Sentence | EASY | 2 | 69% |
| 11 | Count Prefix and Suffix Pairs I | EASY | 2 | 78% |
| 12 | Find Beautiful Indices in the Given Array I | MEDIUM | 2 | 38% |
| 13 | Find Beautiful Indices in the Given Array II | HARD | 2 | 26% |
| 14 | Lexicographically Smallest Generated String | HARD | 2 | 30% |
| 15 | Number of Subarrays That Match a Pattern II | HARD | 2 | 32% |
| 16 | Repeated Substring Pattern | EASY | 2 | 47% |
| 17 | Camelcase Matching | MEDIUM | 1 | 64% |
| 18 | Counting Words With a Given Prefix | EASY | 1 | 85% |
| 19 | Find All Good Strings | HARD | 1 | 44% |
| 20 | Maximum Deletions on a String | HARD | 1 | 35% |
| 21 | Minimum Time to Revert Word to Initial State I | MEDIUM | 1 | 41% |
| 22 | Minimum Time to Revert Word to Initial State II | HARD | 1 | 34% |
You can't drill every string matching variant before the assessment. StealthCoder runs invisibly during screen share and solves whichever variant they throw at you. No browser extension. No detection signature. Built by a senior engineer who knows the OA is theater. This is the script.
Get StealthCoderString Matching problems ask you to locate, count, or validate substrings or patterns. You'll recognize them by keywords like 'find', 'match', 'prefix', 'suffix', 'occur', or 'index'. Common subtypes include prefix-matching (check-if-a-word-occurs-as-a-prefix-of-any-word-in-a-sentence), occurrence-finding (find-the-index-of-the-first-occurrence-in-a-string), and complex pattern validation (find-all-good-strings). Drill order: start with single-pass prefix/suffix logic, move to multi-position searches, then tackle optimizations like KMP or rolling hash for large inputs. Autodesk and Google weight this heavily. If a hard String Matching variant lands in your live OA, StealthCoder reads the problem and solves it in seconds, invisible to the proctor.
Companies that hire most on string matching
22 string matching problems.
You won't drill them all. Pass anyway.
String Matching is one of the patterns interviews actually filter on. Memorizing every variant in a week is a fantasy. StealthCoder is the hedge: an AI overlay invisible during screen share. It reads the problem and surfaces a working solution in under 2 seconds, no matter which string matching flavor lands in your live OA. Built by a senior engineer who knows the OA is theater. This is the script. Works on HackerRank, CodeSignal, CoderPad, and Karat.
String Matching interview FAQ
How many string matching problems should I drill before an OA?+
Focus on the top 8 to 12 core variants first: prefix checks, finding first occurrence, counting all matches, and handling overlaps. With 22 problems tagged here, drilling 10 to 15 will cover most live OA shapes. Autodesk and Capital One especially favor these, so prioritize their patterns if they're on your target list.
What's the simplest way to recognize a string matching problem?+
Look for verbs like 'find', 'match', 'index', 'occur', 'count', or 'prefix'. If the prompt asks you to locate a substring or validate a pattern within a string, it's a match problem. Problems like find-the-index-of-the-first-occurrence-in-a-string are textbook examples.
Do I always need KMP or rolling hash for string matching?+
No. Many problems solve fine with nested loops or built-in string methods. Use KMP or rolling hash when the input size is large or the naive approach times out. Start simple, optimize only if needed. Most OAs reward correct slow code over incorrect fast code.
Which company drills string matching the hardest?+
Autodesk, with 10 problems tagged here, followed by Capital One at 7. Google, Palantir, Visa, and TCS each have 6. If you're interviewing at Autodesk, expect at least one string matching problem in your technical rounds.
How do I handle overlapping matches in string matching?+
Track your position explicitly as you scan the string. After finding a match, decide whether to skip past it entirely or advance by one character to catch overlaps. Problems like find-beautiful-indices-in-the-given-array-i test this logic directly.