3. Longest Substring Without Repeating Characters

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

Example 1:

Input: s = "abcabcbb"
Output: 3
Explanation: The answer is "abc", with the length of 3.

Example 2:

Input: s = "bbbbb"
Output: 1
Explanation: The answer is "b", with the length of 1.

Example 3:

Input: s = "pwwkew"
Output: 3
Explanation: The answer is "wke", with the length of 3.
Notice that the answer must be a substring, "pwke" is a subsequence and not a substring.

Example 4:

Input: s = ""
Output: 0

Constraints:

• 0 <= s.length <= 5 * 104
• s consists of English letters, digits, symbols and spaces.

# @lc code=start
using LeetCode

function length_of_longest_substring(s::String)::Int
    max_string, max_len = "", 0
    for c in s
        # if c occurs twice in max_string
        if c in max_string
            max_string = max_string[(findfirst(c, max_string) + 1):end] * c
        else
            max_string *= c
            max_len = max(length(max_string), max_len)
        end
    end
    return max_len
end
# @lc code=end

length_of_longest_substring (generic function with 1 method)

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