human
Give me a Python code to find the length of the longest substring without repeating characters given the following:
I found an interesting problem on https://leetcode.com/problems/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.

I tried it in Python, but could not do it. Can you solve it?
assistant
#Here is Python code 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