Java LeetCode - Longest Substring Without Repeating Characters Solution

Given a string s, find the length of the longest substring without repeating characters.

Example 1:

Input: s = "abcabcbb"
Output: 3
Explanation: The answer is "abc", with the length of 3.

Example 2:

Input: s = "bbbbb"
Output: 1
Explanation: The answer is "b", with the length of 1.

Example 3:

Input: s = "pwwkew"
Output: 3
Explanation: The answer is "wke", with the length of 3.
Notice that the answer must be a substring, "pwke" is a subsequence and not a substring.

Constraints:

• 0 <= s.length <= 5 X 104
• s consists of English letters, digits, symbols, and spaces.

Solution:

class Solution {
    public int lengthOfLongestSubstring(String s) {
        int[] chars = new int[2 << 6];
        
        int start = 0;
        int end = 0;
        
        int res = 0;
        
        while(end < s.length()) {
            char ch = s.charAt(end);
            chars[ch]++;
            
            while(chars[ch] > 1) {
                char removeChar = s.charAt(start);
                chars[removeChar]--;
                start++;
            }
            
            res = Math.max(res, end - start + 1);
            end++;
        }
        return res;
    }
}