Leetcode Summary...

Sliding Window Problems

76. Minimum Window Substring

438. Find All Anagrams in a String

30. Substring with Concatenation of All Words

3. Longest Substring Without Repeating Characters

159. Longest Substring with At Most Two Distinct Characters

567. Permutation in String

340. Longest Substring with At Most K Distinct Characters

424. Longest Repeating Character Replacement