Find Word sNot In Subsequence
Reported by candidates from Salesfoece's online assessment. Pattern, common pitfall, and the honest play if you blank under the timer.
Salesforce hit you with a string problem in March 2024 that tests whether you can track character state across a sequence. You're given two strings and need to find characters that don't form a valid subsequence pattern. This isn't about searching or sorting. It's about understanding when a character in one string can't be matched sequentially in another. The insight is simple once you see it, but blank on it live and you'll burn 20 minutes. StealthCoder keeps you from guessing.
Pattern and pitfall
The pattern here is string matching with state tracking. You iterate through one string and try to match each character against the other string in order, marking positions as you go. The trick: characters that can't be matched sequentially are your answer. Most candidates try to build a hash of all characters or over-complicate the logic with nested loops. The real solution uses a pointer or index to track your position in the target string, moving forward only when you find a match. If you reach the end of the target without matching a character, that character belongs in your result. Common pitfall is resetting the pointer or comparing character frequency instead of subsequence validity. StealthCoder will show you the exact loop structure to use if you freeze.
Memorize the pattern. If you can't, run StealthCoder. The proctor sees the IDE. They don't see what's behind it.
You can drill Find Word sNot In Subsequence cold, or you can hedge it. StealthCoder runs invisibly during screen share and surfaces a working solution in under 2 seconds. The proctor sees the IDE. They don't see what's behind it. Made by an engineer who treats the OA as theater. If yours is tonight, you don't have time to grind. You have time to hedge.
Get StealthCoderRelated leaked OAs
This OA pattern shows up on LeetCode as is subsequence. If you have time before the OA, drill that.
You've seen the question.
Make sure you actually pass Salesfoece's OA.
Salesfoece reuses patterns across OAs. Made by an engineer who treats the OA as theater. If yours is tonight, you don't have time to grind. You have time to hedge. Works on HackerRank, CodeSignal, CoderPad, and Karat.
Find Word sNot In Subsequence FAQ
Is this actually about subsequences or just character matching?+
It's about subsequences. A subsequence maintains order but doesn't need consecutive characters. So if you're checking whether string A forms a subsequence of string B, you move through B only forward, never backward. That directional constraint is the entire problem.
What's the time complexity I should aim for?+
O(n + m) where n and m are the lengths of the two input strings. Single pass through each, no nested loops. If you're at O(n * m) or worse, you're overcomplicating it.
Do I need to return characters or indices?+
The problem title says 'words not in subsequence,' so you're returning characters (or a string of characters) that can't be matched. Not indices, not counts. Just the actual characters that fail the match.
Should I worry about duplicate characters in the result?+
Only if the problem explicitly says so. Most string subsequence problems want each failing character listed once. Check the expected output format in the examples. If unsure during the OA, list each occurrence separately and adjust if wrong.
Can I solve this without extra space?+
You need at least O(1) or O(k) space for a pointer and maybe a result string. You can't do better than that because you have to return the characters. Don't waste time optimizing space here. Focus on correctness.