LeetCode in Erlang
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
-spec length_of_longest_substring(S :: unicode:unicode_binary()) -> integer().
length_of_longest_substring(S) ->
do(S, 0, #{}, 0, 1).
do(<<Char, Rest/binary>>, Index, PrevPos, Max, Acc0) when is_map_key(Char, PrevPos) ->
PrevIndex = map_get(Char, PrevPos),
Acc1 = Index - PrevIndex,
Acc = min(Acc1, Acc0),
do(Rest, Index + 1, PrevPos#{Char => Index}, max(Max, Acc), Acc + 1);
do(<<Char, Rest/binary>>, Index, PrevPos, Max, Acc) when Acc > Max ->
do(Rest, Index + 1, PrevPos#{Char => Index}, Acc, Acc + 1);
do(<<Char, Rest/binary>>, Index, PrevPos, Max, Acc) ->
do(Rest, Index + 1, PrevPos#{Char => Index}, Max, Acc + 1);
do(<<>>, _, _, Max, _) -> Max.