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.
Follow up: What if the inputs contain unicode characters? How would you adapt your solution to such case?
易位构词游戏的英文词汇是 anagram，这个词来源于有“反向”或“再次”的含义的希腊语字根ana-和有“书写”、“写下”的意思的词根grahpein。易位构词是一类文字游戏（更准确地说是一类“词语游戏”），是将组成一个词或短句的字母重新排列顺序，原文中所有字母的每次出现都被使用一次，这样构造出另外一些新的词或短句。
见程序注释