Permutation in String — C# Coding Problem
Difficulty: medium | Category: sliding-window
Problem Description
Given two strings `s1` and `s2`, return `true` if `s2` **contains a permutation** of `s1`, or `false` otherwise. In other words, return `true` if one of `s1`'s permutations is a substring of `s2`. **Constraints:** - `1 <= s1.length, s2.length <= 10⁴` - `s1` and `s2` consist of lowercase English letters. **Hint:** Use a sliding window of size `len(s1)` over `s2`, maintaining character frequency counts.
Examples
Example 1
Input: s1 = "ab", s2 = "eidbaooo"
Output: true
Explanation: Permutation "ba" is a substring.
Example 2
Input: s1 = "ab", s2 = "eidboaoo"
Output: false