[3] Longest Substring Without Repeating Characters | Leetcode Medium

🔎 問題の説明

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.

せいげんじょうけん

0 <= s.length <= 5 * 10410^4104

s consists of English letters, digits, symbols and spaces.

結論は,アルファベットを繰り返さない最大文字列長を求める問題である.
制限条項のため、暴力を振るうとタイムアウトする可能性があります.これはちょっと難しい問題です.

🧊 Pythonコード

class Solution:
    def lengthOfLongestSubstring(self, s: str) -> int:
        save = []
        max_len = 0
    
        for x in s:
            if x in save:
                save = save[save.index(x)+1:]
            save.append(x)    
            max_len = max(max_len, len(save))
        
        return max_len

各文字をチェックするときに、前の文字であれば、文字列内でその位置に切り取られる前に、そうでなければ文字列の後ろに追加します.各ステップにmax lenを保存します.