Given a string, sort it in decreasing order based on the frequency of characters.
Example 1:
Input: "tree"Output: "eert"Explanation: 'e'appearstwicewhile'r'and't'bothappearonce. So'e'mustappearbeforeboth'r'and't'. Therefore"eetr"isalsoavalidanswer.Example 2:
Input: "cccaaa"Output: "cccaaa"Explanation: Both'c'and'a'appearthreetimes, so"aaaccc"isalsoavalidanswer. Notethat"cacaca"isincorrect, asthesamecharactersmustbetogether.Example 3:
Input: "Aabb"Output: "bbAa"Explanation: "bbaA"isalsoavalidanswer, but"Aabb"isincorrect. Notethat'A'and'a'aretreatedastwodifferentcharacters.这道题是 Google 的面试题。
给定一个字符串，要求根据字符出现的频次从高到低重新排列这个字符串。
思路比较简单，首先统计每个字符的频次，然后排序，最后按照频次从高到低进行输出即可。
