WikiGalaxy
C++ Set
Introduction to C++ Set:
A set in C++ is a part of the Standard Template Library (STL) and is used to store unique elements. It is an associative container that automatically orders its elements.
#include <iostream>
#include <set>
int main() {
std::set<int> mySet;
mySet.insert(1);
mySet.insert(2);
mySet.insert(3);
for (auto it = mySet.begin(); it != mySet.end(); ++it) {
std::cout << *it << " ";
}
return 0;
}
Key Characteristics:
The elements in a set are always unique, and they are stored in a specific order (ascending by default).
Console Output:
1 2 3
Inserting Elements
Inserting Elements:
Elements can be inserted into a set using the insert() function. If the element already exists, it will not be added again.
#include <iostream>
#include <set>
int main() {
std::set<int> mySet;
mySet.insert(5);
mySet.insert(5); // Duplicate, won't be added
mySet.insert(10);
for (auto it = mySet.begin(); it != mySet.end(); ++it) {
std::cout << *it << " ";
}
return 0;
}
Example Explanation:
Attempting to insert a duplicate value (5) does not change the set, as sets do not allow duplicate elements.
Console Output:
5 10
Removing Elements
Removing Elements:
Elements can be removed from a set using the erase() function. You can remove elements by value or by iterator.
#include <iostream>
#include <set>
int main() {
std::set<int> mySet = {1, 2, 3, 4};
mySet.erase(2); // Remove element by value
for (auto it = mySet.begin(); it != mySet.end(); ++it) {
std::cout << *it << " ";
}
return 0;
}
Example Explanation:
The element '2' is removed from the set. The remaining elements are printed in ascending order.
Console Output:
1 3 4
Checking Element Existence
Checking Element Existence:
To check if an element exists in a set, use the find() function. It returns an iterator to the element if found, otherwise it returns the end iterator.
#include <iostream>
#include <set>
int main() {
std::set<int> mySet = {1, 2, 3, 4};
if (mySet.find(3) != mySet.end()) {
std::cout << "3 is in the set" << std::endl;
} else {
std::cout << "3 is not in the set" << std::endl;
}
return 0;
}
Example Explanation:
The find() method checks for the existence of the element '3' in the set. Since it is present, the output confirms its presence.
Console Output:
3 is in the set
Iterating Over a Set
Iterating Over a Set:
You can iterate over elements in a set using iterators, which provide a way to access each element sequentially.
#include <iostream>
#include <set>
int main() {
std::set<int> mySet = {10, 20, 30, 40};
for (auto it = mySet.begin(); it != mySet.end(); ++it) {
std::cout << *it << " ";
}
return 0;
}
Example Explanation:
This example demonstrates how to iterate over a set using an iterator. Each element of the set is accessed in ascending order.
Console Output:
10 20 30 40
Set Size
Set Size:
The size() function returns the number of elements currently stored in the set.
#include <iostream>
#include <set>
int main() {
std::set<int> mySet = {1, 2, 3, 4, 5};
std::cout << "The size of the set is: " << mySet.size() << std::endl;
return 0;
}
Example Explanation:
The size() method is used to determine the number of elements in the set, which is 5 in this example.
Console Output:
The size of the set is: 5
Clearing a Set
Clearing a Set:
The clear() function removes all elements from the set, leaving it empty.
#include <iostream>
#include <set>
int main() {
std::set<int> mySet = {1, 2, 3, 4, 5};
mySet.clear();
std::cout << "The set is now empty with size: " << mySet.size() << std::endl;
return 0;
}
Example Explanation:
After clearing the set, its size becomes 0, indicating that all elements have been removed.
Console Output:
The set is now empty with size: 0
Union of Sets
Union of Sets:
To perform a union of two sets, you can insert elements of one set into another. This combines both sets into one, preserving unique elements.
#include <iostream>
#include <set>
int main() {
std::set<int> set1 = {1, 2, 3};
std::set<int> set2 = {3, 4, 5};
set1.insert(set2.begin(), set2.end());
for (auto it = set1.begin(); it != set1.end(); ++it) {
std::cout << *it << " ";
}
return 0;
}
Example Explanation:
This example demonstrates the union of two sets, resulting in a set containing all unique elements from both sets.
Console Output:
1 2 3 4 5
Intersection of Sets
Intersection of Sets:
To find the intersection of two sets, iterate through one set and check for each element's presence in the other set.
#include <iostream>
#include <set>
int main() {
std::set<int> set1 = {1, 2, 3, 4};
std::set<int> set2 = {3, 4, 5, 6};
std::set<int> resultSet;
for (auto it = set1.begin(); it != set1.end(); ++it) {
if (set2.find(*it) != set2.end()) {
resultSet.insert(*it);
}
}
for (auto it = resultSet.begin(); it != resultSet.end(); ++it) {
std::cout << *it << " ";
}
return 0;
}
Example Explanation:
The intersection operation results in a set containing elements common to both sets, which are '3' and '4'.
Console Output:
3 4
Difference of Sets
Difference of Sets:
The difference between two sets can be found by iterating through one set and inserting elements not found in the other set into a result set.
#include <iostream>
#include <set>
int main() {
std::set<int> set1 = {1, 2, 3, 4};
std::set<int> set2 = {3, 4, 5, 6};
std::set<int> resultSet;
for (auto it = set1.begin(); it != set1.end(); ++it) {
if (set2.find(*it) == set2.end()) {
resultSet.insert(*it);
}
}
for (auto it = resultSet.begin(); it != resultSet.end(); ++it) {
std::cout << *it << " ";
}
return 0;
}
Example Explanation:
The difference operation results in a set containing elements from 'set1' that are not present in 'set2', which are '1' and '2'.
Console Output:
1 2
