add set
This commit is contained in:
+383
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* std::set empty initialization :cpp:set:retrieval:production:
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:PROPERTIES:
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:ANKI_NOTE_TYPE: Basic
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:ANKI_NOTE_ID: 1776613835132
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:END:
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** Front
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Write C++ to create an empty std::set<int>
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** Back
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#+begin_src c++
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std::set<int> s;
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#+end_src
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* std::set initializer list :cpp:set:retrieval:production:
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:PROPERTIES:
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:ANKI_NOTE_TYPE: Basic
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:ANKI_NOTE_ID: 1776613835127
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:END:
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** Front
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Write C++ to create a std::set from initializer list {3, 1, 2}
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** Back
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#+begin_src c++
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std::set<int> s = {3, 1, 2}; // contents: {1, 2, 3} (sorted!)
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#+end_src
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* std::set copy constructor :cpp:set:retrieval:production:
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:PROPERTIES:
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:ANKI_NOTE_TYPE: Basic
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:ANKI_NOTE_ID: 1776613835123
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:END:
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** Front
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Write C++ to copy construct a std::set from existing set s2
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** Back
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#+begin_src c++
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std::set<int> s1(s2); // or: s1 = s2;
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std::set<int> s1 = s2;
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#+end_src
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* std::set from range :cpp:set:retrieval:production:
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:PROPERTIES:
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:ANKI_NOTE_TYPE: Basic
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:ANKI_NOTE_ID: 1776613835120
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:END:
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** Front
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Write C++ to construct std::set from iterator range of another set
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** Back
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#+begin_src c++
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std::set<int> s2(++s1.begin(), s1.end());
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#+end_src
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* std::set C++17 deduction :cpp:set:retrieval:production:
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:PROPERTIES:
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:ANKI_NOTE_TYPE: Basic
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:ANKI_NOTE_ID: 1776613835116
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:END:
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** Front
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Write C++17 deduction guide to create set from another set
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** Back
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#+begin_src c++
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std::set s3 = s2; // deduces std::set<int>
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#+end_src
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* std::set insert return type :cpp:set:retrieval:production:
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:PROPERTIES:
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:ANKI_NOTE_TYPE: Basic
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:ANKI_NOTE_ID: 1776613835112
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:END:
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** Front
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Write C++ to insert 5 into std::set and check if it succeeded
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** Back
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#+begin_src c++
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auto [it, success] = s.insert(5);
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if (!success) {
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// already exists
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}
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#+end_src
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* std::set insert with hint :cpp:set:retrieval:production:
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:PROPERTIES:
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:ANKI_NOTE_TYPE: Basic
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:ANKI_NOTE_ID: 1776613835107
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:END:
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** Front
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Write C++ to insert 5 near begin() as a hint
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** Back
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#+begin_src c++
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s.insert(s.begin(), 5); // returns iterator only (C++11+)
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#+end_src
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* std::set emplace vs insert :cpp:set:retrieval:production:
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:PROPERTIES:
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:ANKI_NOTE_TYPE: Basic
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:ANKI_NOTE_ID: 1776613835103
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:END:
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** Front
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Write C++ to emplace {5, 6} directly into a std::set without copying
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** Back
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#+begin_src c++
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s.emplace(5); // constructs in-place
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s.emplace(std::piecewise_construct,
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std::forward_as_tuple(5),
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std::forward_as_tuple());
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#+end_src
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* std::set erase by key :cpp:set:retrieval:production:
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:PROPERTIES:
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:ANKI_NOTE_TYPE: Basic
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:ANKI_NOTE_ID: 1776613835099
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:END:
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** Front
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Write C++ to erase key 5 from std::set and check count removed
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** Back
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#+begin_src c++
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size_t n = s.erase(5); // returns count erased (0 or 1)
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#+end_src
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* std::set erase by iterator :cpp:set:set:retrieval:production:
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:PROPERTIES:
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:ANKI_NOTE_TYPE: Basic
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:ANKI_NOTE_ID: 1776613835095
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:END:
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** Front
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Write C++ to erase element at iterator it
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** Back
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#+begin_src c++
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it = s.erase(it); // returns iterator to next element
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#+end_src
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* std::set erase range :cpp:set:retrieval:production:
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:PROPERTIES:
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:ANKI_NOTE_TYPE: Basic
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:ANKI_NOTE_ID: 1776613835091
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:END:
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** Front
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Write C++ to erase all elements from begin() to end()
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** Back
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#+begin_src c++
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s.erase(s.begin(), s.end()); // clears entire set
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#+end_src
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* std::set find :cpp:set:retrieval:production:
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:PROPERTIES:
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:ANKI_NOTE_TYPE: Basic
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:ANKI_NOTE_ID: 1776613835088
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:END:
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** Front
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Write C++ to check if key 5 exists in set using find()
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** Back
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#+begin_src c++
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if (s.find(5) != s.end()) {
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// found
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}
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#+end_src
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* std::set count :cpp:set:retrieval:production:
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:PROPERTIES:
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:ANKI_NOTE_TYPE: Basic
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:ANKI_NOTE_ID: 1776613835084
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:END:
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** Front
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Write C++ to check if key 5 exists using count() (set returns 0 or 1)
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** Back
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#+begin_src c++
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if (s.count(5) == 1) {
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// exists
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}
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#+end_src
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* std::set contains (C++20) :cpp:set:retrieval:production:
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:PROPERTIES:
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:ANKI_NOTE_TYPE: Basic
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:ANKI_NOTE_ID: 1776613835079
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:END:
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** Front
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Write C++20 to check if key 5 exists using contains()
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** Back
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#+begin_src c++
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if (s.contains(5)) {
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// found
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}
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#+end_src
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* std::set extract (C++17) :cpp:set:retrieval:production:
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:PROPERTIES:
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:ANKI_NOTE_TYPE: Basic
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:ANKI_NOTE_ID: 1776613835075
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:END:
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** Front
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Write C++ to extract key 5 from set and reinsert it
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** Back
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#+begin_src c++
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auto node = s.extract(5); // removes and returns node_handle
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s.insert(std::move(node));
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#+end_src
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* std::set merge (C++17) :cpp:set:retrieval:production:
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:PROPERTIES:
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:ANKI_NOTE_TYPE: Basic
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:ANKI_NOTE_ID: 1776613835072
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:END:
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** Front
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Write C++ to merge elements from set s2 into s1
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** Back
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#+begin_src c++
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s1.merge(s2); // transfers matching elements from s2 to s1
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#+end_src
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* std::set begin/end iterators :cpp:set:iterators:retrieval:production:
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:PROPERTIES:
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:ANKI_NOTE_TYPE: Basic
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:ANKI_NOTE_ID: 1776613835067
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:END:
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** Front
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Write C++ to iterate over all elements in std::set
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** Back
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#+begin_src c++
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for (const auto& elem : s) {
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std::cout << elem << '\n';
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}
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// or with iterators:
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for (auto it = s.begin(); it != s.end(); ++it) {
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std::cout << *it << '\n';
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}
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#+end_src
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* std::set reverse iterators :cpp:set:iterators:retrieval:production:
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:PROPERTIES:
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:ANKI_NOTE_TYPE: Basic
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:ANKI_NOTE_ID: 1776613835062
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:END:
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** Front
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Write C++ to iterate backwards through std::set
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** Back
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#+begin_src c++
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for (auto it = s.rbegin(); it != s.rend(); ++it) {
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std::cout << *it << '\n'; // prints in descending order
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}
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#+end_src
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* std::set const_iterator :cpp:set:iterators:retrieval:production:
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:PROPERTIES:
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:ANKI_NOTE_TYPE: Basic
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:ANKI_NOTE_ID: 1776613835057
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:END:
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** Front
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Write C++ to get const_iterator to first element
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** Back
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#+begin_src c++
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std::set<int>::const_iterator it = s.cbegin(); // C++11+
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auto it = s.cbegin(); // auto also works
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#+end_src
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* std::set lower_bound :cpp:set:lookup:retrieval:production:
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:PROPERTIES:
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:ANKI_NOTE_TYPE: Basic
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:ANKI_NOTE_ID: 1776613835053
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:END:
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** Front
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Write C++ to find first element >= 5 in std::set
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** Back
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#+begin_src c++
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auto it = s.lower_bound(5);
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if (it != s.end() && *it == 5) {
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// found exact match
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}
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#+end_src
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* std::set upper_bound :cpp:set:lookup:retrieval:production:
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:PROPERTIES:
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:ANKI_NOTE_TYPE: Basic
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:ANKI_NOTE_ID: 1776613835049
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:END:
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** Front
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Write C++ to find first element > 5 in std::set
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** Back
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#+begin_src c++
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auto it = s.upper_bound(5); // skips past all elements == 5
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#+end_src
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* std::set equal_range :cpp:set:lookup:retrieval:production:
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:PROPERTIES:
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:ANKI_NOTE_TYPE: Basic
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:ANKI_NOTE_ID: 1776613835045
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:END:
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** Front
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Write C++ to get pair of iterators for elements matching 5
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** Back
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#+begin_src c++
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auto [lo, hi] = s.equal_range(5);
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// lo = lower_bound(5), hi = upper_bound(5)
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if (lo != hi) {
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// found element(s)
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}
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#+end_src
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* std::set insert multiple from initializer list :cpp:set:retrieval:production:
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:PROPERTIES:
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:ANKI_NOTE_TYPE: Basic
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:ANKI_NOTE_ID: 1776613835042
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:END:
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** Front
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Write C++ to insert multiple elements {1, 2, 3} at once
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** Back
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#+begin_src c++
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s.insert({1, 2, 3});
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// or with pair return (C++17):
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auto [it, success] = s.insert({1, 2, 3});
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#+end_src
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* std::set key_comp and value_comp :cpp:set:observers:retrieval:production:
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:PROPERTIES:
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:ANKI_NOTE_TYPE: Basic
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:ANKI_NOTE_ID: 1776613835037
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:END:
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** Front
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Write C++ to get the comparison object from std::set
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** Back
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#+begin_src c++
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std::set<int>::key_compare comp = s.key_comp();
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std::set<int>::value_compare vcomp = s.value_comp(); // same for set
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#+end_src
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* std::set empty and size :cpp:set:capacity:retrieval:production:
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:PROPERTIES:
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:ANKI_NOTE_TYPE: Basic
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:ANKI_NOTE_ID: 1776613835032
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:END:
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** Front
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Write C++ to check if set is empty and get size
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** Back
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#+begin_src c++
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bool b = s.empty();
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size_t n = s.size();
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size_t max = s.max_size();
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#+end_src
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* std::set clear :cpp:set:retrieval:production:
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:PROPERTIES:
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:ANKI_NOTE_TYPE: Basic
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:ANKI_NOTE_ID: 1776613835028
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:END:
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** Front
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Write C++ to remove all elements from std::set
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** Back
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#+begin_src c++
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s.clear(); // equivalent to s.erase(s.begin(), s.end())
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#+end_src
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* std::set swap :cpp:set:retrieval:production:
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:PROPERTIES:
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:ANKI_NOTE_TYPE: Basic
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:ANKI_NOTE_ID: 1776613835025
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:END:
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** Front
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Write C++ to swap contents of two sets
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** Back
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#+begin_src c++
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s1.swap(s2); // or: s1.swap(s2);
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std::swap(s1, s2);
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#+end_src
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* std::set O(log n) operations summary :cpp:set:complexity:retrieval:understanding:
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:PROPERTIES:
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:ANKI_NOTE_TYPE: Basic
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:ANKI_NOTE_ID: 1776613835020
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:END:
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** Front
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What is the time complexity of insert, find, erase in std::set?
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** Back
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O(log n) for all operations. std::set is implemented as a red-black tree.
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* std::set properties :cpp:set:retrieval:understanding:
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:PROPERTIES:
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:ANKI_NOTE_TYPE: Basic
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:ANKI_NOTE_ID: 1776613835015
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:END:
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** Front
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What are the key properties of std::set?
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** Back
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- No duplicate keys (use std::multiset for duplicates)
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- Keys are sorted (ascending by default)
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- Implemented as red-black tree
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- Elements cannot be modified through iterators (const)
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