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