Distinct Subsequences

HardDynamic ProgrammingDynamic Programming

Solve this the way you would in the interview: out loud, on a timer, with an AI interviewer asking follow-ups while you code. You get a scored report at the end.

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Problem

Given two strings s and t, return the number of distinct subsequences of s which equals t. The test cases are generated so that the answer fits on a 32-bit signed integer.

Examples

Input: s = "rabbbit", t = "rabbit"
Output: 3
Input: s = "babgbag", t = "bag"
Output: 5

Constraints

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

What the interviewer grades

A correct solution is one of five scores. The report also grades problem understanding (did you clarify inputs and edge cases before coding), problem solving, communication while you work, code quality, and testing. See a sample report, or read up on the pattern in the lessons.

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