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C++ Unordered_map Library - empty() Function
Description
The C++ function std::unordered_map::empty() tests whether unordered_map is empty or not. Unordered_map of size zero is considered as empty unordered_map.
Declaration
Following is the declaration for std::unordered_map::empty() function form std::unordered_map header.
C++11
bool empty() const noexcept;
Parameters
None
Return value
Returns true if map is empty otherwise false.
Exceptions
This member function never throws exception.
Time complexity
Constant i.e. O(1)
Example
The following example shows the usage of std::unordered_map::empty() function.
#include <iostream> #include <unordered_map> using namespace std; int main(void) { unordered_map<char, int> um; if (um.empty()) cout << "Unordered map is empty" << endl; um.emplace('a', 1); if (!um.empty()) cout << "Unordered map is not empty" << endl; return 0; }
Let us compile and run the above program, this will produce the following result −
Unordered map is empty Unordered map is not empty
unordered_map.htm
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