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🔥BPE Token Pair Frequency (Tokenizer Engine)Medium
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BPE Token Pair Frequency (Tokenizer Engine)

Targeted in FAANG & Tech OA:GoogleAmazonMicrosoft
Real-World Engineering Context
Core subword vocabulary generation step used by OpenAI's tiktoken and Hugging Face tokenizers.
In Byte-Pair Encoding (BPE), tokenizers repeatedly merge the most frequent adjacent character pair. Given an array of space-separated token strings `words` and a target 2-element pair `[char1, char2]`, count how many times this exact adjacent pair appears across all words.

Sample Test Cases

Input: [["l o w","l o w e r"],["l","o"]]
Expected: 2
Input: [["a b a b","a b c"],["a","b"]]
Expected: 3

Constraints

  • 1 <= words.length <= 1000
  • pair.length == 2
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