unordered_set

• std::unordered_set is an associative container that contains a set of unique objects. Search, insertion, and removal operations have average constant-time complexity.

Initialization

• Empty Unordered Set:

std::unordered_set<int> myUnorderedSet;

Insert Elements

• Insert Single Element (Average case O(1)):

myUnorderedSet.insert(10); // Insert an element

• Emplace Element (Average case O(1)):

myUnorderedSet.emplace(10); // Construct and insert element

Access Elements

• Find Element (Average case O(1)):

auto it = myUnorderedSet.find(10);
// Returns iterator to the element if found, otherwise returns myUnorderedSet.end()

Removing Elements

• Remove Element by Value (Average case O(1)):

myUnorderedSet.erase(10); // Erases element with value 10

Query Attributes

• Get Unordered Set Size (O(1)):

size_t size = myUnorderedSet.size(); // Returns the number of elements

• Check if Unordered Set is Empty (O(1)):

bool isEmpty = myUnorderedSet.empty(); // Returns true if unordered set is empty, otherwise false

Iterating through Unordered Set

• Using Iterator (O(n)):

for (auto it = myUnorderedSet.begin(); it != myUnorderedSet.end(); ++it) {
    // Access the element as *it
}

• Using Range-based For Loop (O(n)):

for (const auto& elem : myUnorderedSet) {
    // Access the element directly as elem
}

Other Common Operations

• Clear Unordered Set (O(n)):

myUnorderedSet.clear(); // Removes all elements from the unordered set