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59 lines
1.3 KiB
Python
59 lines
1.3 KiB
Python
"""
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567. Permutation in String
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Difficulty: Medium
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https://leetcode.com/problems/permutation-in-string/
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──────────────────────────────────────────────────
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Given two strings s1 and s2, return true if s2 contains a permutation
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of s1, or false otherwise.
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In other words, return true if one of s1's permutations is the
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substring of s2.
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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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"""
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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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