Distinct Subsequences: coding question

Problem

You get two strings s and t. Return the number of distinct subsequences of s that are equal to t.

A subsequence of s is a string that you get when you remove zero or more characters from s. The remaining characters keep their order.

Two subsequences are distinct when they use different sets of positions in s. The answer fits in a signed 32-bit integer.

Input:: s = "banana", t = "ban"
Output:: 3
Explanation:: The b is at index 0. The a and the n are at indexes 1 and 2, at 1 and 4, or at 3 and 4.

Input:: s = "abc", t = "abcd"
Output:: 0
Explanation:: t is longer than s, so no subsequence of s is equal to t.

SysRound wrote this statement. A reference solution checks every example.

Continue with questions that share topics or the same question type.

Decode Ways
Coding · Dynamic Programming · String
Generate Parentheses
Coding · Backtracking · Bracket Sequences · Dynamic Programming
Longest Common Subsequence
Coding · Dynamic Programming · Longest Common Subsequence · String
Longest Palindromic Subsequence
Coding · Dynamic Programming · String

Sources · 2 references

These records explain where the question appears. A company tag or candidate report does not guarantee a future interview question.

Hello Interview · 1 record

No company association
Leetcode 115. Distinct Subsequences
Reported date not specified · 0 source reports
Source snapshot: Nov 12, 2026
View source

LeetCode company tags · 2 records

Problem

You get two strings s and t. Return the number of distinct subsequences of s that are equal to t.

A subsequence of s is a string that you get when you remove zero or more characters from s. The remaining characters keep their order.

Two subsequences are distinct when they use different sets of positions in s. The answer fits in a signed 32-bit integer.

Input:: s = "banana", t = "ban"
Output:: 3
Explanation:: The b is at index 0. The a and the n are at indexes 1 and 2, at 1 and 4, or at 3 and 4.

Input:: s = "abc", t = "abcd"
Output:: 0
Explanation:: t is longer than s, so no subsequence of s is equal to t.

SysRound wrote this statement. A reference solution checks every example.