Valid Anagram Given two strings s and t, write a function to determine if t is an anagram of s. For example, s = “anagram”, t = “nagaram”, return true. s = “rat”, t = “car”, return false. Note: You may assume the string contains only lowercase alphabets. use sort […]

Given a pattern and a string str, find if str follows the same pattern. Here follow means a full match, such that there is a bijection between a letter in pattern and a non-empty word in str. Examples: pattern = “abba”, str = “dog cat cat dog” should return true. […]

Expression Tree Build The structure of Expression Tree is a binary tree to evaluate certain expressions. All leaves of the Expression Tree have an number string value. All non-leaves of the Expression Tree have an operator string value. Now, given an expression array, build the expression tree of this expression, […]