Hi, For "Longest Substring with K Distinct Characters" question, curious to know why map is used? also below solution with set is correct? please clarify. Thanks

static int findLongestSubString(String input, int K) { if (input == null || input.length() == 0 || input.length() < K) throw new IllegalArgumentException(); int maxCount = Integer.MIN_VALUE; int windowStart = 0; Set store = new HashSet(); for(int i = 0; i < input.length(); i++) { Character currentChar = input.charAt(i); store.add(currentChar); while(store.size() > K) { store.remove(input.charAt(windowStart)); windowStart++; } maxCount = Math.max(maxCount, (i - windowStart) + 1); } return (maxCount == Integer.MIN_VALUE) ? 0 : maxCount; }