The C++ function std::unordered_map::unordered_map() constructs an unordered_map with the contents of other using move semantics.
Following is the declaration for std::unordered_map::unordered_map() function form std::unordered_map header.
unordered_map(unordered_map&& um);
um − Another unordered_map object of same type.
Constructor never returns value.
Constant i.e. O(1)
The following example shows the usage of std::unordered_map::unordered_map() function.
#include <iostream> #include <unordered_map> using namespace std; int main(void) { unordered_map<char, int> um1 = { {'a', 1}, {'b', 2}, {'c', 3}, {'d', 4}, {'e', 5} }; unordered_map<char, int>um2(move(um1)); cout << "Unordered_map contains following elements" << endl; for (auto it = um2.begin(); it != um2.end(); ++it) cout << it->first << " = " << it->second << endl; return 0; }
Let us compile and run the above program, this will produce the following result −
Unordered_map contains following elements e = 5 a = 1 b = 2 c = 3 d = 4