Given two strings `s` and `t`, return the number of distinct subsequences of `s` which equals `t`.
A subsequence of a string is obtained by deleting zero or more characters from the original string while keeping the relative order of the remaining characters. The test cases are guaranteed to fit in a 32-bit signed integer.
Example 1
Input:s = "rabbbit", t = "rabbit"
Output:3
Explanation:There are three ways to form rabbit from rabbbit by deleting one b (positions 2, 3, or 4).
Example 2
Input:s = "babgbag", t = "bag"
Output:5
Constraints
- 1 <= s.length, t.length <= 1000
- s and t consist of English letters.