Find the longest substring without repeating characters
Sliding Window is a subarray running on a large array, which is a collection of underlying elements. Here we use two pointers, one pointer A always selects the first char of the max substring, from each iteration of the string. The second pointer B runs ahead of pointer A, until a duplicate character is found or the end of the string is reached. public int lengthOfLongestSubstring(String s) { int a_pointer = 0; int b_pointer = 0; int max = 0; Set<Character> hashSet = new HashSet<>(); int i = 0; while(b_pointer < s.length()) { if(!hashSet.contains(s.charAt(b_pointer))) { hashSet.add(s.charAt(b_pointer)); b_pointer++; max = Math.max(hashSet.size(), max); } else { hashSet.remove(s.charAt(a_pointer)); a_pointer++; } } return max; }