Practice Count Palindromic Subsequences
Read the task, work through the examples, and check your approach against the constraints. Use the original LeetCode task for coding and submissions.
Problem Statement
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 10^9 + 7.
Source: Count Palindromic Subsequences on LeetCode. Use the original task for its coding environment and submissions.
Examples
# Example 1
Input
s = "103301"
Output
2
# Example 2
Input
s = "0000000"
Output
21
# Example 3
Input
s = "9999900000"
Output
2
Constraints
1 <= s.length <= 10^4
s consists of digits.
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