Leetcode 392. Is Subsequence

Check whether string s can be obtained from t by deleting some characters without reordering (i.e., whether s is a subsequence of t), typically solved with a greedy two-pointer scan in O(|t|+|s|). For many queries, preprocess t (e.g., build a next-occurrence table or char→sorted indices) to answer each s quickly by jumping to the next matching positions.