class Solution:
    def lengthOfLongestSubstring(self, s: str) -> int:
        count = 0
        current = []
        solutions = {}
        for c in s:
            if c in current:
                solutions[count] = current
                idx = current.index(c)
                current = current[idx + 1:]
                count -= idx + 1
            current.append(c)
            count += 1
        solutions[count] = current
        return max(solutions.keys())