public member function
<unordered_map>

std::unordered_map::clear

void clear() noexcept;
Clear content
All the elements in the unordered_map container are dropped: their destructors are called, and they are removed from the container, leaving it with a size of 0.

Parameters

none

Return value

none

Example

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// clearing unordered_map
#include <iostream>
#include <string>
#include <unordered_map>

int main ()
{
  std::unordered_map<std::string,std::string> mymap =
         { {"house","maison"}, {"car","voiture"}, {"grapefruit","pamplemousse"} };

  std::cout << "mymap contains:";
  for (auto& x: mymap) std::cout << " " << x.first << "=" << x.second;
  std::cout << std::endl;

  mymap.clear();
  mymap["hello"]="bonjour";
  mymap["sun"]="soleil";

  std::cout << "mymap contains:";
  for (auto& x: mymap) std::cout << " " << x.first << "=" << x.second;
  std::cout << std::endl;

  return 0;
}


Possible output:
mymap contains: house=maison grapefruit=pamplemousse car=voiture
mymap contains: sun=soleil hello bonjour

Complexity

Linear on size (destructors).

Iterator validity

All iterators, pointers and references are invalidated.

See also