LengthOfLongestSubstring

Problem

https://leetcode.com/problems/longest-substring-without-repeating-characters/

Given a string s, find the length of the longest substring without repeating characters.

Solution

The longest substring can start from any position in the string. So, we must iterate through each position in the entire string. For each position, we look right until we find a duplicate character. At each iteration, if the current substring is longer than the longest, we update the length of the longest substring. Once we find a duplicate character, reset the seen characters.

Code

def lengthOfLongestSubstring(s: str) -> int:
    """Finds the length of the longest substring without repeating characters.
    """
    longest_len = 0
    for i in range(len(s)):
        j = i
        seen_chars = set()
        curr_len = 0
        while j < len(s):
            char = s[j]
            if char in seen_chars:
                break
            else:
                curr_len += 1
                seen_chars.add(char)
                j += 1

            longest_len = max(longest_len, curr_len)

    return longest_len

Test

>>> from LengthOfLongestSubstring import lengthOfLongestSubstring
>>> lengthOfLongestSubstring('abcabcbb')
3
>>> lengthOfLongestSubstring('bbbbb')
1
>>> lengthOfLongestSubstring('pwwkew')
3

LengthOfLongestSubstring.lengthOfLongestSubstring(s: str) → int

Finds the length of the longest substring without repeating characters.