Longest Substring with At Most Two Distinct Characters

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Given a string, find the length of the longest substring T that contains at most 2 distinct characters.

For example,Given s = “eceba”,

T is "ece" which its length is 3.

思路：同向双指针，跟Longest Substring with At Most K Distinct Characters 一模一样，i是主指针，j是辅指针，然后模板套起来，注意要判断如果即将要大于k的时候，j停下来，不做任何事情，update res，然后i++；代码跟K一模一样，只是把k改成2即可；

class Solution {public int lengthOfLongestSubstringTwoDistinct(String s) {if(s == null || s.length() == 0) {return 0;}char[] ss = s.toCharArray();int[] scount = new int[256];int C = 0;int j = 0;int maxlen = 0;for(int i = 0; i < ss.length; i++) {// move j;while(j < ss.length && C <= 2) {if(scount[ss[j]] == 0) {if(C == 2) {break;}C++;}scount[ss[j]]++;j++;}// update result;// 最多是k，小于k也必须update maxlen；if(j - i > maxlen) {maxlen = j - i;}// remove i;scount[ss[i]]--;if(scount[ss[i]] == 0) {C--;}}return maxlen;}
}

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