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Two pointers, scan both strings once, done.
Start by clarifying the problem and edge cases, then propose a two-pointer approach that iterates through t while advancing a pointer in s when characters match. Analyze time and space complexity, and discuss potential optimizations or alternative approaches like binary search for multiple queries.
Pro tip: Mention that for multiple queries with the same t, you can preprocess t to create a mapping of character positions and use binary search to answer each query in O(|s| log |t|) time, which is more efficient than the O(|s|+|t|) two-pointer approach per query.
Restate the problem in your own words and ask clarifying questions about input constraints, character sets, and expected output. Confirm that subsequence means characters appear in order but not necessarily consecutively.
Identify edge cases such as empty strings, s longer than t, and identical strings. Explain how your solution handles them.
Describe the two-pointer approach: iterate through t with index j, and for each character in s, advance j until a match is found or t is exhausted. If all characters of s are matched, return true; otherwise false.
State that the time complexity is O(|s| + |t|) and space complexity is O(1). Explain that each character in t is visited at most once.
Mention that for multiple queries with the same t, preprocessing t with a hash map of character positions and binary search can reduce per-query time to O(|s| log |t|). Also note that if s is very small, the two-pointer approach is optimal.
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