Package g0901_1000.s0940_distinct_subsequences_ii

Class Solution

  • All Implemented Interfaces:
    
public final class Solution

    940 - Distinct Subsequences II\.

    Hard

    Given a string s, return the number of distinct non-empty subsequences of s. Since the answer may be very large, return it modulo <code>10<sup>9</sup> + 7</code>.

    A 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 <code>"<ins>a</ins>b<ins>c</ins>d<ins>e</ins>"</code> while "aec" is not.

    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", "aa", "ba", and "aba".

    Example 3:

    Input: s = "aaa"

    Output: 3

    Explanation: The 3 distinct subsequences are "a", "aa" and "aaa".

    Constraints:

    • 1 &lt;= s.length &lt;= 2000

    • s consists of lowercase English letters.

    • Nested Class Summary

      Nested Classes 
      Modifier and Type Class Description

    • Field Summary

      Fields 
      Modifier and Type Field Description

    • Constructor Summary

      Constructors 
      Constructor Description
      Solution()

    • Enum Constant Summary

      Enum Constants 
      Enum Constant Description

    • Method Summary

      Modifier and Type Method Description
      final Integer distinctSubseqII(String s)

      • Methods inherited from class java.lang.Object

        clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait