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52 lines
1.1 KiB
Plaintext
52 lines
1.1 KiB
Plaintext
---
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title: '567. Permutation in String'
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description: Given two strings s1 and s2, return true if s2 contains a permutation of s1, or false otherwise
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sidebar:
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label: 'Permutation in String'
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badge: 'Medium'
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---
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<Badge variant="accent">Sliding Window</Badge>
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### Example 1:
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- Input: `s1 = "ab", s2 = "eidbaooo"`
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- Output: `true`
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- Explanation: `s2` contains one permutation of `s1` ("ba").
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### Example 2:
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- Input: `s1 = "ab", s2 = "eidboaoo"`
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- Output: `false`
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### Constraints:
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- `1 <= s1.length, s2.length <= 10^4`
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- `s1` and `s2` consist of lowercase English letters.
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## Solution
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```py
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from collections import Counter
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class Solution:
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def checkInclusion(self, s1: str, s2: str) -> bool:
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k = len(s1)
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if k > len(s2):
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return False
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need = Counter(s1)
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window = Counter()
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for right, c in enumerate(s2):
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window[c] += 1
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if right >= k:
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left_char = s2[right - k]
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window[left_char] -= 1
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if window[left_char] == 0:
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del window[left_char]
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if window == need:
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return True
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return False
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```
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