Leetcode 刷题 – 排序（day3）_桶排序_按照字符出现次数对字符串排序

2. 按照字符出现次数对字符串排序
451. Sort Characters By Frequency (Medium)

Input: “tree” Output: “eert” Explanation: ‘e’ appears twice while ‘r’ and ‘t’ both appear once. So ‘e’ must appear before both ‘r’ and ‘t’. Therefore “eetr” is also a valid answer.

实现思路：
1.建立map字典，统计字符串中每个元素出现的次数2.建立集合数组，以map中的值为集合数组下表，map的键为集合数组元素3.将集合数组从大到小赋值给新集合。因为可能r数组中的某些值为null，故要进行该操作
字符串方法简介

/** * 用StringBuilder，StringBuffer，Lis

Leetcode 刷题 – 排序（day3）_桶排序_按照字符出现次数对字符串排序最先出现在Python成神之路。