CF915F-Imbalance Value of a Tree 题目: 题目描述: You are given a tree T consisting of n vertices. A number is written on each vertex; the number written on vertex i is ai . Let’s denote the function I(x,y) as the difference between maximum and minimum value of ai on a simple path
CF985F-Isomorphic Strings 题目: 题目描述: You are given a string s of length n consisting of lowercase English letters. For two given strings s and t , say S is the set of distinct characters of s and T is the set of distinct characters of t . The