Given a string of digits s, return the number of palindromic subsequences of s having length 5. Since the answer may be very large, return it modulo 109 + 7.
Note:
\n\n\n
Example 1:
\n\n\nInput: s = "103301"\nOutput: 2\nExplanation: \nThere are 6 possible subsequences of length 5: "10330","10331","10301","10301","13301","03301". \nTwo of them (both equal to "10301") are palindromic.\n\n\n
Example 2:
\n\n\nInput: s = "0000000"\nOutput: 21\nExplanation: All 21 subsequences are "00000", which is palindromic.\n\n\n
Example 3:
\n\n\nInput: s = "9999900000"\nOutput: 2\nExplanation: The only two palindromic subsequences are "99999" and "00000".\n\n\n
\n
Constraints:
\n\n1 <= s.length <= 104s consists of digits.Compiled with clang 11 using the latest C++ 20 standard.
Your code is compiled with level two optimization (-O2). AddressSanitizer is also enabled to help detect out-of-bounds and use-after-free bugs.
Most standard library headers are already included automatically for your convenience.
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