395. Longest Substring with At Least K Repeating Characters

Find the length of the longest substring T of a given string (consists of lowercase letters only) such that every character in T appears no less than k times.

Example 1:

Input:
s = "aaabb", k = 3

Output:
3

The longest substring is "aaa", as 'a' is repeated 3 times.

Example 2:

Input:
s = "ababbc", k = 2

Output:
5

The longest substring is "ababb", as 'a' is repeated 2 times and 'b' is repeated 3 times.

 题目的意思是找最长的子字符串T，在T中每个字母出现的次数都不少于k，返回结果是T的长度。

思路：

一，用HashMap找到每个字母出现的次数；

二，如果每个字母出现的次数都不小于k，那么直接返回s的长度即可，否则，如果一个字母出现次数小于k，那T一定不包含这个字符，那么就可以以出现次数小于k的字母作为分隔符；

三，将分割后的子字符串重复步骤一，二。

主要参考了这篇博客。代码如下：

//map用于记录每个character出现的次数
		Map map = new HashMap<>();
		for(int i=0;i

PS：很多天没写博客了啊==