Package g0901_1000.s0940_distinct_subsequences_ii

Class Solution

java.lang.Object
g0901_1000.s0940_distinct_subsequences_ii.Solution
public class Solution extends java.lang.Object
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 109 + 7.

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 "abcde" 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 <= s.length <= 2000
  • s consists of lowercase English letters.

  • Constructor Summary

    Constructors
    Constructor
    Description
    Solution()
     

  • Method Summary

    Modifier and Type
    Method
    Description
    int
    distinctSubseqII(java.lang.String str)
     

    Methods inherited from class java.lang.Object

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

  • Constructor Details

    • Solution

      public Solution()

  • Method Details

    • distinctSubseqII

      public int distinctSubseqII(java.lang.String str)