leetcode: 3. Longest Substring Without Repeating Characters

# Given a string, find the length of the longest substring without repeating characters.
#
# Examples:
#
# Given "abcabcbb", the answer is "abc", which the length is 3.
#
# Given "bbbbb", the answer is "b", with the length of 1.
#
# Given "pwwkew", the answer is "wke", with the length of 3. 
# Note that the answer must be a substring, "pwke" is a subsequence and not a substring.

class Solution():
    def lengthOfLongestSubstring(self, s):
        longest, start, visited = 0, 0, [False for _ in range(256)]
        for ind, val in enumerate(s):
            if not visited[ord(val)]:
                visited[ord(val)] = True
                longest = max(longest, ind-start+1)
            else:
                while s[start] != val:
                    visited[ord(s[start])] = False
                    start += 1
                start += 1
        return longest


if __name__ == '__main__':
    assert Solution().lengthOfLongestSubstring('abcabcbb') == 3
    assert Solution().lengthOfLongestSubstring('bbbb') == 1
    assert Solution().lengthOfLongestSubstring('pwwkew') == 3

class Solution():
    def lengthOfLongestSubstring(self, s):
        longest = 0
        i, j = 0, 1
        while j < len(s):
            if len(''.join(list(set(s[i:j+1])))) == len(s[i:j+1]):
                if len(s[i:j+i]) > longest:
                    longest = len(s[i:j+1])
                j += 1
            else:
                i += 1
        return longest