Analysis of LeetCode High Frequency Problems IV Posted on 2020-02-12 Edited on 2020-02-20 In Algorithms Note Views: Symbols count in article: 172 详细讲解LeetCode考察较多的3道题目：336、340、407。 336.Palindrome Pairs(回文对)(Hard)340.longest Substring with at most k distinct characters(至多包含K个不同字符的最长子串)(Hard)407.Trapping rain water ii(接雨水 II)(Hard)