human
Solve in Python:
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.

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Can you provide a Python program to find the length of the longest substring without repeating characters?
assistant
#Here is Python program to find the length of the longest substring without repeating characters.

class Solution:
     def lengthOfLongestSubstring(self, s):
         """
         :type s: str
         :rtype: int
         """
         result = 0
         if len(s) == 0:
             return result
         
         hashmap = {}
         start = 0
         for i in range(len(s)):
             if s[i] in hashmap:
                 start = max(hashmap[s[i]] + 1,start)
             hashmap[s[i]] = i
             result = max(result,i-start+1)
         return result