map operator= in C++ STL

The map::operator= is a built function in C++ STL which assigns contents of a container to a different container, replacing its current content. 

Syntax:

map1_name = map2_name

Parameters: The map on the left is the container in which the map on the right is to be assigned by destroying the elements of map1. 

Return Value: This function does not return anything. 

CPP

// C++ program for illustration of
// map::operator= function
#include <bits/stdc++.h>
using namespace std;

int main()
{

    // initialize container
    map<int, int> mp, copymp;

    // insert elements in random order
    mp.insert({ 2, 30 });
    mp.insert({ 1, 40 });
    mp.insert({ 4, 50 });

    // = operator is used to copy map
    copymp = mp;

    // prints the elements
    cout << "\nThe map mp is : \n";
    cout << "KEY\tELEMENT\n";
    for (auto itr = mp.begin(); itr != mp.end(); ++itr) {
        cout << itr->first
             << '\t' << itr->second << '\n';
    }

    cout << "\nThe map copymap is : \n";
    cout << "KEY\tELEMENT\n";
    for (auto itr = copymp.begin(); itr != copymp.end(); ++itr) {
        cout << itr->first
             << '\t' << itr->second << '\n';
    }
    return 0;
}

Output:

The map mp is : 
KEY    ELEMENT
1    40
2    30
4    50

The map copymap is : 
KEY    ELEMENT
1    40
2    30
4    50

Time Complexity : O(n*log n) , Where n is the number of inserted elements 
Auxiliary Space : O(n)