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

Example 1:

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3

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

Example 2:

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3

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:

1 2	Input: s = "" Output: 0

最長不重複子字串，沒看過的加入set, 跟最長size比較更新最大值，看過就從set刪除。

Java

Time: O(n), Space: O(1)
class Solution {
    public int lengthOfLongestSubstring(String s) {

        int i = 0, j = 0, max = 0;
        // Upcasting allowed to access only parent class members and child class specified members
        Set<Character> set = new HashSet<>();
        
        while (j < s.length()) { // O(1)
            if (!set.contains(s.charAt(j))) { // O(1), O(1)
                set.add(s.charAt(j++)); // O(1) ++ to next
                max = Math.max(max, set.size());
            } else {
                set.remove(s.charAt(i++)); // O(1)
            }
        }       
        return max;
    }
}

Python

Time: O(n), Space: O(1)

class Solution:
    def lengthOfLongestSubstrig(self, s:str) -> int:
      characters = set()
      left=right=ans=0
      length=len(s)

      while right < length:
        print(characters, right, left, ans)
        if s[right] in characters:
          characters.remove(s[left])
          left+=1
        else:
          characters.add(s[right])
          right+=1
          ans = max(ans,right-left)
      return ans
print(Solution().lengthOfLongestSubstrig('abcabcbb'))

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Lunski's Clutter

3. Longest Substring Without Repeating Characters

Java

Python