{ "data": { "question": { "questionId": "977", "questionFrontendId": "940", "boundTopicId": null, "title": "Distinct Subsequences II", "titleSlug": "distinct-subsequences-ii", "content": "

Given a string s, return the number of distinct non-empty subsequences of s. Since the answer may be very large, return it modulo 109 + 7.

\nA subsequence of a string is a new string that is formed from the original string by deleting some (can be none) of the characters without disturbing the relative positions of the remaining characters. (i.e., "ace" is a subsequence of "abcde" while "aec" is not.\n

 

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Example 1:

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\nInput: s = "abc"\nOutput: 7\nExplanation: The 7 distinct subsequences are "a", "b", "c", "ab", "ac", "bc", and "abc".\n
\n\n

Example 2:

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\nInput: s = "aba"\nOutput: 6\nExplanation: The 6 distinct subsequences are "a", "b", "ab", "aa", "ba", and "aba".\n
\n\n

Example 3:

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\nInput: s = "aaa"\nOutput: 3\nExplanation: The 3 distinct subsequences are "a", "aa" and "aaa".\n
\n\n

 

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Constraints:

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