LeetCode in Elixir
3. Longest Substring Without Repeating Characters
Medium
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 * 104sconsists of English letters, digits, symbols and spaces.
Solution
defmodule Solution do
@spec length_of_longest_substring(s :: String.t()) :: integer
def length_of_longest_substring(s) do
sublen([], String.codepoints(s), 0, 0, 0)
end
defp sublen(_, [], _, _, m), do: m
defp sublen(left, [next | rest] = right, start, stop, m) do
if Enum.member?(left, next) do
[_ | mid] = left
sublen(mid, right, start + 1, stop, m)
else
stop = stop + 1
sublen(left ++ [next], rest, start, stop, max(m, stop - start))
end
end
end