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 * 104
• s consists of English letters, digits, symbols and spaces.

Solution:

class Solution(object):
    def lengthOfLongestSubstring(self, s):

        mapSet = {}
        start, result = 0, 0

        for end in range(len(s)):
        	if s[end] in mapSet:
        		start = max(mapSet[s[end]], start)
        	result = max(result, end-start+1)
        	mapSet[s[end]] = end+1

        return result