Distinct Subsequences II
Given a string s, return the number of distinct non-empty subsequences of s. Since the answer may be very large, return it modulo 10^9 + 7.
A subsequence of a string is a new string formed from the original string by deleting some characters, possibly none, without disturbing the relative positions of the remaining characters. For example, "ace" is a subsequence of "abcde", while "aec" is not.
Example 1
Input
s = "abc"Output
7The 7 distinct subsequences are "a", "b", "c", "ab", "ac", "bc", and "abc".
Example 2
Input
s = "aba"Output
6The 6 distinct subsequences are "a", "b", "ab", "aa", "ba", and "aba".
Constraints
- 1 <= s.length <= 2000
- s consists of lowercase English letters.