C++ map - swap() Function
The C++ map swap() function is used to exchange all elements of one map with all elements of another map. To apply this function, the data-type of both maps must be same, although the size may differ.
Syntax
template<class Key, class T, class Compare, class Alloc>
void swap(
map<Key,T,Compare,Alloc>& lhs,
map<Key,T,Compare,Alloc>& rhs
);
template<class Key, class T, class Compare, class Alloc>
void swap(
map<Key,T,Compare,Alloc>& lhs,
map<Key,T,Compare,Alloc>& rhs
);
Parameters
lhs |
First map. |
rhs |
Second map. |
Return Value
None.
Time Complexity
Constant i.e, Θ(1).
Example:
In the example below, the swap() function is used to exchange all elements of map MyMap1 with all elements of map MyMap2.
#include <iostream>
#include <map>
using namespace std;
int main (){
map<string, int> MyMap1;
map<string, int> MyMap2;
map<string, int>::iterator it;
//elements of MyMap1
MyMap1["John"] = 2500;
MyMap1["Jack"] = 2600;
MyMap1["Ella"] = 2000;
//elements of MyMap2
MyMap2["Nora"] = 3000;
MyMap2["Adam"] = 3100;
cout<<"Before Swapping, The MyMap1 contains:\n";
for(it = MyMap1.begin(); it != MyMap1.end(); ++it)
cout<<it->first<<" "<<it->second<<"\n";
cout<<"\nBefore Swapping, The MyMap2 contains:\n";
for(it = MyMap2.begin(); it != MyMap2.end(); ++it)
cout<<it->first<<" "<<it->second<<"\n";
swap(MyMap1, MyMap2);
cout<<"\n\nAfter Swapping, The MyMap1 contains:\n";
for(it = MyMap1.begin(); it != MyMap1.end(); ++it)
cout<<it->first<<" "<<it->second<<"\n";
cout<<"\nAfter Swapping, The MyMap2 contains:\n";
for(it = MyMap2.begin(); it != MyMap2.end(); ++it)
cout<<it->first<<" "<<it->second<<"\n";
return 0;
}
The output of the above code will be:
Before Swapping, The MyMap1 contains: Ella 2000 Jack 2600 John 2500 Before Swapping, The MyMap2 contains: Adam 3100 Nora 3000 After Swapping, The MyMap1 contains: Adam 3100 Nora 3000 After Swapping, The MyMap2 contains: Ella 2000 Jack 2600 John 2500
❮ C++ <map> Library
