Given a string s, find the length of the longest substring without repeating characters.
0 <= s.length <= 5 * 10^4, s consists of English letters, digits, symbols and spaces
Use sliding window with a hash set or map. Expand right, and when duplicate found, shrink from left until no duplicates.
def lengthOfLongestSubstring(s):
char_set = set()
left = 0
max_len = 0
for right in range(len(s)):
while s[right] in char_set:
char_set.remove(s[left])
left += 1
char_set.add(s[right])
max_len = max(max_len, right - left + 1)
return max_len