159. Longest Substring with At Most Two Distinct Characters

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https://leetcode.com/problems/longest-substring-with-at-most-two-distinct-characters/

String: Sliding Window

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class Solution {
    public int lengthOfLongestSubstringTwoDistinct(String s) {
        int len=s.length();
        if(len<3)return len;
        
        int left=0,right=0;
        HashMap<Character,Integer> hashmap=new HashMap<>();
        int maxLen=2;
        while(right<len){
            if(hashmap.size()<3) hashmap.put(s.charAt(right),right++);
            if(hashmap.size()==3){
                int delIdx=Collections.min(hashmap.values());
                hashmap.remove(s.charAt(delIdx));
                left=delIdx+1;
            }
            maxLen=Math.max(maxLen,right-left);
        }
        return maxLen;
    }
}

LeetCode Explanation

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