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Distinct Subsequences is a hard coding interview question covering dynamic programming, strings — the kind asked at FAANG (Facebook/Meta, Apple, Amazon, Netflix, Google) and AI-first companies like Anthropic, OpenAI, and Nvidia.
Given strings s and t, return the number of distinct subsequences of s that equal t.
Example: s="rabbbit", t="rabbit" -> 3 (three ways to choose which "b" to drop) Example: s="babgbag", t="bag" -> 5
A subsequence is formed by deleting some (possibly zero) characters from s without changing the relative order.
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