Solution: Minimum Window Subsequence

Explore the sliding window technique to efficiently solve the minimum window subsequence problem. Learn to find the shortest substring in one string that contains all characters of another string in order, optimize your approach from naive to efficient solutions, and grasp the underlying logic to handle subsequence matching with minimal time complexity.

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Statement
Solution
- Naive approach
- Optimized approach using sliding window

Statement

Given two strings, s1 and s2, find and return the shortest substring of s1 in which all the characters of s2 appear in the same order, but not necessarily next to each other (i.e., s2 should be a subsequence of the substring).

If no such substring exists, return an empty string "". If there are multiple shortest substrings, return the one that appears first in s1 (i.e., with the left-most starting index).

Note: A substring is a contiguous sequence of characters within a string. A subsequence is a sequence of characters that can be derived from a string by deleting some characters without changing the order of the remaining characters. For example, “edu” is a substring and “cave” is a subsequence of “educative.”

Constraints:

$1 \leq$ s1.length $\leq 2 \times 10^{3}$
$1 \leq$ s2.length $\leq 100$
s1 and s2 consist of uppercase and lowercase English letters.