std::unordered_set::operator=

From cppreference.com
unordered_set& operator=( const unordered_set& other );
(1) (since C++11)
unordered_set& operator=( unordered_set&& other );
(2) (since C++11)

Replaces the contents of the container.

1) Copy assignment operator. Replaces the contents with a copy of the contents of other.

2) Move assignment operator. Replaces the contents with those of other using move semantics (i.e. the data in other is moved from other into this container). other is in a valid but unspecified state afterwards.

Contents

[edit] Parameters

other - another container to be used as source

[edit] Return value

*this

[edit] Complexity

1) Linear in the size of the container.

2) Constant.

[edit] Example

The following code uses to assign one std::unordered_set to another:

#include <unordered_set>
#include <iostream>
 
void display_sizes(const std::unordered_set<int> &nums1,
                   const std::unordered_set<int> &nums2,
                   const std::unordered_set<int> &nums3)
{
    std::cout << "nums1: " << nums1.size() 
              << " nums2: " << nums2.size()
              << " nums3: " << nums3.size() << '\n';
}
 
int main()
{
    std::unordered_set<int> nums1 {3, 1, 4, 6, 5, 9};
    std::unordered_set<int> nums2; 
    std::unordered_set<int> nums3;
 
    std::cout << "Initially:\n";
    display_sizes(nums1, nums2, nums3);
 
    // copy assignment copies data from nums1 to nums2
    nums2 = nums1;
 
    std::cout << "After assigment:\n"; 
    display_sizes(nums1, nums2, nums3);
 
    // move assignment moves data from nums1 to nums3,
    // modifying both nums1 and nums3
    nums3 = std::move(nums1);
 
    std::cout << "After move assigment:\n"; 
    display_sizes(nums1, nums2, nums3);
}

Output:

Initially:
nums1: 6 nums2: 0 nums3: 0
After assigment:
nums1: 6 nums2: 6 nums3: 0
After move assigment:
nums1: 0 nums2: 6 nums3: 6

[edit] See also

constructs the unordered_set
(public member function)