115. Distinct Subsequences

Hard

String,Dynamic Programming

---

Given two strings s and t, return the number of distinct subsequences of s which equals t.

A string's subsequence is a new string formed from the original string by deleting some (can be none) of the characters without disturbing the remaining characters' relative positions. (i.e., "ACE" is a subsequence of "ABCDE" while "AEC" is not).

The test cases are generated so that the answer fits on a 32-bit signed integer.

 

Example 1:

Input: s = "rabbbit", t = "rabbit"
Output: 3
Explanation:
As shown below, there are 3 ways you can generate "rabbit" from S.
rabbbit
rabbbit
rabbbit

Example 2:

Input: s = "babgbag", t = "bag"
Output: 5
Explanation:
As shown below, there are 5 ways you can generate "bag" from S.
babgbag
babgbag
babgbag
babgbag
babgbag

 

Constraints:

• 1 <= s.length, t.length <= 1000
• s and t consist of English letters.

---

Submissions

Time Submitted	Status	Runtime	Memory	Language
08/16/2022 21:48	Accepted	17 ms	15 MB	cpp
08/04/2022 20:41	Accepted	25 ms	15.1 MB	cpp
08/04/2022 20:24	Accepted	11 ms	15.1 MB	cpp
08/04/2022 20:23	Time Limit Exceeded	N/A	N/A	cpp
08/04/2022 20:22	Runtime Error	N/A	N/A	cpp
08/04/2022 20:22	Accepted	1095 ms	30.1 MB	cpp
08/04/2022 20:20	Runtime Error	N/A	N/A	cpp
09/19/2021 13:24	Accepted	304 ms	18.6 MB	cpp