unique_len_3_palindrome.py (1094B)
| # 1930. Unique Length-3 Palindromic Subsequences
import string
"""
given a string 's', return the number of unique palindromes of length three
that that are a subsequence of 's'. note that even if there are multiple ways
to obtain the same subsequence, it is still only counted once. a palindrome
is a string that reads the same forwards and backwards. a subsequence of a
string is a new string generated from the original string with some
characters (can be none) deleted without changing the relative order of thhe
remaining characters. for example: "ace" is a subsequence of "abcde"
"""
class Solution(object):
def countPalindromicSubsequence(self, s):
ans = 0
for c in string.ascii_lowercase:
i, j = s.find(c), s.rfind(c)
if i > -1:
ans += len(set(s[i + 1 : j]))
return ans
if __name__ == "__main__":
obj = Solution()
print(obj.countPalindromicSubsequence("aabca")) # expect: 3
print(obj.countPalindromicSubsequence("adc")) # expect: 0
print(obj.countPalindromicSubsequence("bbcbaba")) # expect: 4
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