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Showing content from https://cplusplus.com/reference/map/map/empty/ below:

public member function

<map>

std::map::empty 
bool empty() const noexcept;

Test whether container is empty

Returns whether the map container is empty (i.e. whether its size is 0).

This function does not modify the container in any way. To clear the content of a map container, see map::clear.



Parameters none

Return Valuetrue if the container size is 0, false otherwise.

Example 
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// map::empty
#include <iostream>
#include <map>

int main ()
{
  std::map<char,int> mymap;

  mymap['a']=10;
  mymap['b']=20;
  mymap['c']=30;

  while (!mymap.empty())
  {
    std::cout << mymap.begin()->first << " => " << mymap.begin()->second << '\n';
    mymap.erase(mymap.begin());
  }

  return 0;
}

Output:


Complexity Constant.

Iterator validity No changes.

Data races The container is accessed.
No contained elements are accessed: concurrently accessing or modifying them is safe.

Exception safetyNo-throw guarantee: this member function never throws exceptions.

See also
map::clear
Clear content (public member function)
map::erase
Erase elements (public member function)
map::size
Return container size (public member function)

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