22 lines
608 B
Org Mode
22 lines
608 B
Org Mode
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#+ANKI_DECK: study_deck_02
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#+TITLE: DSA Tricks & Patterns
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* Task: Count character frequencies faster than map :dsa:counting:array:string:retrieval::production:
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:PROPERTIES:
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:ANKI_NOTE_TYPE: Basic
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:ROADMAP: [[file:../roadmap.org::*0242. Valid Anagram][0242. Valid Anagram]]
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:END:
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** Front
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Write C++ to count character frequencies in a string using a
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fixed-size array instead of ~std::map~ (assume lowercase a-z only).
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** Back
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#+begin_src cpp
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std::array<int, 26> freq{};
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for (char c : s) freq[c - 'a']++;
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#+end_src
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*Why:* O(1) per access vs O(log n) for ~std::map~. Use when alphabet
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is bounded and small.
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