unordered_multimap clear() function in C++ STL

The unordered_multimap::clear() is a built-in function in C++ STL which clears the contents of the unordered_multimap container. The final size of the container after the call of the function is 0.

Syntax:

unordered_multimap_name.clear()

Parameters: The function does not accept any parameter.

Return Value: It returns nothing.

Below programs illustrates the above function:

Program 1:

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// C++ program to illustrate the
// unordered_multimap::clear()
#include <bits/stdc++.h>
using namespace std;
  
int main()
{
  
    // declaration
    unordered_multimap<int, int> sample;
  
    // inserts key an delement
    sample.insert({ 10, 100 });
    sample.insert({ 10, 100 });
    sample.insert({ 20, 200 });
    sample.insert({ 30, 300 });
    sample.insert({ 15, 150 });
  
    cout << "Key and Elements of multimap are:";
  
    for (auto it = sample.begin(); it != sample.end(); it++) {
        cout << "\n{" << it->first << ", " << it->second << "}";
    }
  
    sample.clear();
  
    cout << "\nSize of container after function call: "
         << sample.size();
  
    return 0;
}

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Output:

Key and Elements of multimap are:
{15, 150}
{30, 300}
{20, 200}
{10, 100}
{10, 100}
Size of container after function call: 0

Program 2:

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// C++ program to illustrate the
// unordered_multimap::clear()
#include <bits/stdc++.h>
using namespace std;
  
int main()
{
  
    // declaration
    unordered_multimap<char, char> sample;
  
    // inserts element
    sample.insert({ 'a', 'b' });
    sample.insert({ 'a', 'b' });
    sample.insert({ 'b', 'c' });
    sample.insert({ 'r', 'a' });
    sample.insert({ 'c', 'b' });
  
    cout << "Key and Elements of multimap are:";
  
    for (auto it = sample.begin(); it != sample.end(); it++) {
        cout << "\n{" << it->first << ", " << it->second << "}";
    }
  
    sample.clear();
  
    cout << "\nSize of container after function call: "
         << sample.size();
    return 0;
}

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Output:

Key and Elements of multimap are:
{c, b}
{r, a}
{b, c}
{a, b}
{a, b}
Size of container after function call: 0


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