Greedy on string
Last updated: November 22, 2025
Quick Overview
Given a string, implement a greedy algorithm to determine the longest substring that can be formed by removing at most one character. The function should return the length of this substring. For example, given the input "abca", the output should be 3, as removing 'b' or 'c' results in the valid substrings "aca" or "aba".
Compass
November 22, 202535
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2,669 solved
Given a string, implement a greedy algorithm to determine the longest substring that can be formed by removing at most one character. The function should return the length of this substring. For example, given the input "abca", the output should be 3, as removing 'b' or 'c' results in the valid substrings "aca" or "aba".
Coding interviews at Compass 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
- What happens if the input contains duplicates?
- What is the worst-case input for your solution?
- Can you solve this in a single pass?
- How would you modify your solution to handle streaming input?
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Problem Analysis
To solve the problem of finding the longest substring that can be formed by removing at most one character, we can utilize the two pointers technique. This approach is applicable here because we n...
Approach
- Initialize two pointers,
leftat the start of the string andrightat the end. - Move the
leftpointer to the right until characters at theleftandrightpointers do not match. If a mis...
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