import java.util.*;

public class longestSubstringTwoDistinct {

public static void main(String[] args){

longestSubstringTwoDistinct obj = new longestSubstringTwoDistinct();

String s = "ecebaaaaae";

System.out.println(obj.longest(s));

}

/* Given a string s, find the length of the longest substring t that contains at most 2 distinct characters

注意是 "AT MOST"，比"EXACTLY EQUAL"简单一些

* */

private int longest(String s){

int res = 0;

if(s == null || s.length() == 0){

return 0;

}

Map<Character, Integer> map = new HashMap<>();

int count = 0; // how many distinct characters in substring

for(int left = 0, right = 0; right < s.length(); right ++){

map.putIfAbsent(s.charAt(right), 0);

if(map.get(s.charAt(right)) == 0){

count ++;

}

map.put(s.charAt(right),map.get(s.charAt(right))+1);

while(left <= right && count > 2){

map.put(s.charAt(left), map.get(s.charAt(left)) - 1);

if(map.get(s.charAt(left)) == 0){

count --;

}

left ++;

}

System.out.println(s.substring(left, right+1));

res = Math.max(res, right-left+1);

}

return res;

}

}