[HashTable] LeetCode: 3. Longest Substring Without Repeating Characters

https://leetcode.com/problems/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.

 

Constraints:

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

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투 포인터로 윈도우 사이즈를 조절하면서 슬라이딩 윈도우 이동을 통해 중복 없는 문자열의 최대 길이를 구하였다.

 

class Solution:
    def lengthOfLongestSubstring(self, s: str) -> int:
    	used = {}       
        max_length = start = 0
        
        for idx, char in enumerate(s):
        	# 이미 등장한 문자인 경우 left pointer(start) 위치 갱신
            if char in used:
            	start = used[char] + 1
            # 처음 보는 문자인 경우 최대 문자열 길이 갱신
            else:
            	max_length = max(max_length, idx - start + 1)
            
            used[char] = idx
        
        return max_length