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dynamic_programming/longest_palindromic_subsequence.py
44 строки
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Sanket Kittad
Palindromic (#9288)
05 окт 2023, 02:40
Не верифицирован
05 окт 2023, 02:40
1fda96b
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""" author: Sanket Kittad Given a string s, find the longest palindromic subsequence's length in s. Input: s = "bbbab" Output: 4 Explanation: One possible longest palindromic subsequence is "bbbb". Leetcode link: https://leetcode.com/problems/longest-palindromic-subsequence/description/ """ def longest_palindromic_subsequence(input_string: str) -> int: """ This function returns the longest palindromic subsequence in a string >>> longest_palindromic_subsequence("bbbab") 4 >>> longest_palindromic_subsequence("bbabcbcab") 7 """ n = len(input_string) rev = input_string[::-1] m = len(rev) dp = [[-1] * (m + 1) for i in range(n + 1)] for i in range(n + 1): dp[i][0] = 0 for i in range(m + 1): dp[0][i] = 0 # create and initialise dp array for i in range(1, n + 1): for j in range(1, m + 1): # If characters at i and j are the same # include them in the palindromic subsequence if input_string[i - 1] == rev[j - 1]: dp[i][j] = 1 + dp[i - 1][j - 1] else: dp[i][j] = max(dp[i - 1][j], dp[i][j - 1]) return dp[n][m] if __name__ == "__main__": import doctest doctest.testmod()