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68 lines
1.8 KiB
Plaintext
68 lines
1.8 KiB
Plaintext
---
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title: '3. Longest Substring Without Repeating Characters'
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description: Given a string s, find the length of the longest substring without duplicate characters
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icon: line-dot-left-horizontal
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sidebar:
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label: 'Longest Substring Without Repeating Characters'
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badge: 'Medium'
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---
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<Badge variant="accent">Hash Table</Badge>
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### Example 1:
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- Input: `s = "abcabcbb"`
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- Output: `3`
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- Explanation: The answer is "abc", with the length of `3`. Note that "bca" and "cab" are also correct answers.
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### Example 2:
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- Input: `s = "bbbbb"`
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- Output: `1`
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- Explanation: The answer is "b", with the length of `1`.
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### Example 3:
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- Input: `s = "pwwkew"`
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- Output: `3`
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- 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.
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### Constraints:
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- `0 <= s.length <= 10^5`
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- `s` consists of English letters, digits, symbols and spaces.
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## Approach
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```mermaid
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flowchart TD
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S(["lengthOfLongestSubstring(s)"]) --> I["left = 0, ans = 0, window = set()"]
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I --> L{"more (right, c) in s?"}
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L -- no --> E(["return ans"])
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L -- yes --> W{"c already in window?"}
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W -- yes --> P["window.remove(s[left]); left += 1 — shrink until c is free"]
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P --> W
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W -- no --> A["window.add(c)"]
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A --> M["ans = max(ans, right - left + 1)"]
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M --> L
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```
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## Solution
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```py
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class Solution:
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def lengthOfLongestSubstring(self, s: str) -> int:
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left = 0
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ans = 0
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window = set()
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for right, c in enumerate(s):
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while c in window:
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window.remove(s[left])
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left += 1
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window.add(c)
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ans = max(ans, right - left + 1)
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return ans
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```
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## Explanation
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<YouTube id="wiGpQwVHdE0" title="Longest Substring Without Repeating Characters - Leetcode 3 - Python" />
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