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Given a string s, count the number of distinct, non-empty subsequences of s .

Since the result may be large, return the answer modulo 109 + 7.

 

Example 1:

Input: s = "abc"
Output: 7
Explanation: The 7 distinct subsequences are "a", "b", "c", "ab", "ac", "bc", and "abc".

Example 2:

Input: s = "aba"
Output: 6
Explanation: The 6 distinct subsequences are "a", "b", "ab", "ba", "aa" and "aba".

Example 3:

Input: s = "aaa"
Output: 3
Explanation: The 3 distinct subsequences are "a", "aa" and "aaa".

 

 

Note:

  1. s contains only lowercase letters.
  2. 1 <= s.length <= 2000

 

 

class Solution { public int distinctSubseqII(String s) { } }