Two-pointer skipping once on mismatch is the move.
Use a two-pointer technique starting from both ends of the string. When characters mismatch, check if skipping either the left or right character results in a palindrome. If either does, return true; otherwise, return false.
Pro tip: Clarify edge cases upfront, such as empty strings or strings with one character, and mention that the solution runs in O(n) time with O(1) space. This shows attention to detail and efficiency.
Confirm that deleting at most one character means zero or one deletion is allowed, and that the string can be empty or have any length. Ask if the string contains only lowercase letters or any characters.
Initialize two pointers at the start and end of the string. Move them inward while characters match. If a mismatch occurs, try skipping the left character or the right character and check if the remaining substring is a palindrome.
Write a helper function that checks if a substring (given by indices) is a palindrome using two pointers. This avoids code duplication.
When a mismatch is found, call the helper on the substring excluding the left character and on the substring excluding the right character. If either returns true, the answer is true.
State that the time complexity is O(n) because each character is visited at most twice, and space complexity is O(1). Discuss edge cases like empty string, single character, and strings that are already palindromes.
AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.
First, clarify the original problem and the current solution's complexity. Then, explain how allowing K deletions changes the problem, likely requiring a dynamic programming approach with a state dimension for deletions. Finally, discuss the time and space complexity trade-offs and potential optimizations.
Pro tip: Demonstrate awareness that K deletions often turns a simple two-pointer problem into a DP problem, but also mention that if K is small, you might still use a modified sliding window with a counter. This shows you consider constraints before jumping to a solution.
Restate the problem with K deletions and ask about constraints: is K fixed, what are the input sizes, and what is the expected complexity? This ensures you're solving the right problem.
Briefly describe the original solution for one deletion (e.g., two-pointer or DP) and its complexity. This sets a baseline for comparison.
Explain that with K deletions, a greedy two-pointer may not work; instead, use dynamic programming with states (i, j, k) where k is deletions used. Define the recurrence and base cases.
State the time and space complexity (e.g., O(n*m*K)) and discuss optimizations like reducing space to O(m*K) or using early termination if K is small.
Mention trade-offs between DP and other approaches (e.g., BFS for edit distance), and handle edge cases like K >= length of string.
AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.