Solution: Minimum Window Subsequence

Explore how to solve the minimum window subsequence problem by applying an optimized sliding window approach. Understand how to traverse and backtrack pointers efficiently to find the smallest substring in one string that contains all characters of another string in order, improving time complexity while minimizing extra space.

We'll cover the following...

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 $\leq 100$ ...