Given a string s, return the number of different non-empty palindromic subsequences in
s. Since the answer may be very large, return it modulo
109 + 7.
A subsequence of a string is obtained by deleting zero or more characters from the string.
A sequence is palindromic if it is equal to the sequence reversed.
a1, a2, ... and
b1, b2, ... are different if there is some
i for which
ai != bi.
Input: s = "bccb" Output: 6 Explanation: The 6 different non-empty palindromic subsequences are 'b', 'c', 'bb', 'cc', 'bcb', 'bccb'. Note that 'bcb' is counted only once, even though it occurs twice.
Input: s = "abcdabcdabcdabcdabcdabcdabcdabcddcbadcbadcbadcbadcbadcbadcbadcba" Output: 104860361 Explanation: There are 3104860382 different non-empty palindromic subsequences, which is 104860361 modulo 109 + 7.
1 <= s.length <= 1000