Detect subsequence in string
Last updated: November 8, 2025
Quick Overview
Given a string and a subsequence, determine if the subsequence can be found within the string while maintaining the order of characters. The function should return a boolean value indicating whether the subsequence exists in the string. For example, given the string "abcde" and the subsequence "ace", the output should be true.
Supabase
November 8, 202533
4
794 solved
Given a string and a subsequence, determine if the subsequence can be found within the string while maintaining the order of characters. The function should return a boolean value indicating whether the subsequence exists in the string. For example, given the string "abcde" and the subsequence "ace", the output should be true.
Coding interviews at Supabase focus on problem-solving approach as much as the final solution. The interviewer wants to see you break down the problem, consider edge cases, and optimize iteratively. Communication throughout the process is key.
What the Interviewer Expects
- Recognize the underlying problem pattern (sliding window, two pointers, BFS/DFS, etc.)
- Discuss multiple approaches and trade-offs before coding
- Implement an optimal solution with clean, production-quality code
- Handle all edge cases including boundary conditions and invalid input
- Optimize both time and space complexity with clear justification
- Test your solution systematically with well-chosen examples
Key Topics to Cover
How to Approach This
- Clarify input constraints and edge cases before writing code.
- Walk through your approach verbally and confirm with the interviewer before coding.
- Start with a brute force solution, then optimize. Mention time and space complexity.
- Test your solution with examples, including edge cases like empty input or duplicates.
- Consider common patterns: sliding window, two pointers, hash map, BFS/DFS, dynamic programming.
Possible Follow-up Questions
- How would you parallelize this solution?
- What happens if the input contains duplicates?
- How would your solution change if the input was sorted?
- What is the worst-case input for your solution?
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Problem Analysis
The problem of detecting whether a subsequence exists within a given string can be efficiently solved using the two pointers technique. This approach is applicable here because we need to traverse...
Approach
- Initialize two pointers:
ifor the string andjfor the subsequence. Start both at zero. - Loop through the string using the
ipointer:- If the character at
str[i]matchessubseq[j],...
- If the character at
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