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C++ set operator=There are following three uses of operator= in set:
Syntaxcopy(1) set& operator= (const set& x); //until C++ 11 copy (1) set& operator= (const set& x); //since C++ 11 move (2) set& operator= (set&& x); //since C++ 11 initializer list (3) set& operator= (initializer_list<value_type> il); //since C++ 11 copy (1):- Copies all the elements from x into the set container. move (2):- Moves the content of x into the set container. initializer_list (3):- Copies the elements of il into the set container. Parameterx: A set object with the same type. il: An initializer list object. Return valuethis pointer. ComplexityCopy assignment: Linear in sizes. Move assignment: Linear in current container size. Initializer list assignment: Up to logarithmic in sizes. Iterator validityAll references, iterators and pointers related to this set are invalidated. Data RacesAll copied elements are accessed. The move assignment modifies x. The set container and all its elements are modified. Exception SafetyIf an exception is thrown, the container is in a valid state. Example 1Let's see the simple example to copy the content of one set to another: #include <iostream> #include <set> using namespace std; int main(void) { set<int> s1 = {10,20,30}; cout << "Set s1 contains following elements" << endl; for (auto it = s1.begin(); it != s1.end(); ++it) cout << *it << endl; set<int> s2 = s1; cout<<"\nAfter Copying the elements from s1 to s2... \n"; cout << "\nSet s2 contains following elements" << endl; for (auto it = s2.begin(); it != s2.end(); ++it) cout << *it<< endl; return 0; } Output: Set s1 contains following elements 10 20 30 After copying the elements from s1 to s2... Set s2 contains following elements 10 20 30 In the above example, operator = is used to copy the content of one set s1 to another set s2. Example 2Let's see a simple example to move the elements of one set to another: #include <iostream> #include <set> using namespace std; int main(void) { set<char> s1 = {'a','e','i','o','u'}; cout << "Set m1 contains following elements" << endl; for (auto it = s1.begin(); it != s1.end(); ++it) cout << *it << ", "; set<char> s2 = move(s1); cout<<"\n\nAfter moving the elements from s1 to s2... \n"; cout << "\nSet s2 contains following elements" << endl; for (auto it = s2.begin(); it != s2.end(); ++it) cout << *it << ", "; return 0; } Output: Set m1 contains following elements a, e, i, o, u, After moving the elements from s1 to s2? Set s2 contains following elements a, e, i, o, u, In the above example, operator = is used to move the content of one set s1 to another set s2. Example 3Let's see a simple example to copy the content from initializer list to set: #include <iostream> #include <set> using namespace std; int main(void) { set<int> s; s = {100, 200, 300, 400, 500}; //initializer list cout << "Set contains the following elements" << endl; for (auto it = s.begin(); it != s.end(); ++it) cout << *it << endl; return 0; } Output: Set contains the following elements 100 200 300 400 500 In the above example, operator = is used to copy the content from initializer list to set m. Example 4Let's see a simple example: #include <iostream> #include <set> using namespace std; int main () { int values [] = { 5 , 2 , 4 , 1 , 0 , 0 , 9 }; set < int > c1 ( values , values + 7 ); set < int > c2 ; c2 = c1 ; c1 = set < int > (); cout<< "Size Of c1:" << c1 . size () << endl ; cout<< "Size Of c2:" << c2 . size () << endl ; } Output: Size Of c1:0 Size Of c2:6 In the above example, there are two sets c1 and c2. c1 has 7 elements and c2 is empty, but after assigning c1 to c2, size of c1 become 0 and size of c2 become 7.
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