find the length of the longest substring in it with no more than K distinct characters.

LongestSubStringWithKDistinctChar.java

public class LongestSubStringWithKDistinctChar{

	//O(N + K)
	public int findLength(String str, int K) {
		int windowStart = 0, maxLen = 0;
		
		var dict = new HashMap<Character, Integer>();
		for(int i = 0; i < str.length(); i++){
			char rightChar = str.charAt(i);
			dict.put(rightChar, dict.getOrDefault(rightChar, 0) + 1);

			while(dict.size() > K){
				char leftChar = str.charAt(windowStart);
				dict.put(leftChar, dict.get(leftChar) - 1);
				if(dict.get(leftChar) == 0){
					dict.remove(leftChar);
				}
				windowStart++;
			}

			maxLen = Math.max(maxLen, (i-windowStart)+1);
		}
		return maxLen;
	}

}