3.py

classSolution(object):
deflengthOfLongestSubstring(self, s):
"""
 :type s: str
 :rtype: int
 """
#Edge
ifnots:
return0

start, max_length, hash=0, 0, {}

fori, numinenumerate(s):
# Need to have the following condition:
# start <= hash[num] to avoid edge case such as :
# "tmmzuxt"
ifnuminhashandstart<=hash[num]:
#update pointer
start=hash[num] +1
else:
max_length=max(max_length, i-start+1)

hash[num] =i

returnmax_length