sliding window

Easy

Number	Note
121. Best Time to Buy and Sell Stock	minPrice and maxProfit, find the profit for each
219. Contains Duplicate II

Medium

Number	Note
3. Longest Substring Without Repeating Characters
209. Minimum Size Subarray Sum
424. Longest Repeating Character Replacement
438. Find All Anagrams in a String
567. Permutation In String
658. Find K Closest Elements

Hard

Number	Note
76. Minimum Window Substring
239. Sliding Window Maximum

Optional