unordered_multimap count() function in C++ STL

The unordered_multimap::count() is a built-in function in C++ STL which returns the number of elements in the container whose key is equal to the key passed in the parameter.

Syntax:

unordered_multimap_name.count(key)

Parameters: The function accepts a single mandatory parameter key which specifies the key whose count in the unordered_multimap container is to be returned.



Return Value: It returns an unsigned integral type which denotes the number of times a key occurs in the container.

Below programs illustrates the above function:

Program 1:

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// C++ program to illustrate the
// unordered_multimap::count()
#include <bits/stdc++.h>
using namespace std;
  
int main()
{
  
    // declaration
    unordered_multimap<int, int> sample;
  
    // inserts key and element
    sample.insert({ 10, 100 });
    sample.insert({ 10, 100 });
    sample.insert({ 20, 200 });
    sample.insert({ 30, 300 });
    sample.insert({ 30, 150 });
  
    cout << "10 occurs " << sample.count(10) 
         << " times";
  
    cout << "\n20 occurs " << sample.count(20) 
         << " times";
  
    cout << "\n13 occurs " << sample.count(13) 
         << " times";
  
    cout << "\n30 occurs " << sample.count(30) 
         << " times";
  
    return 0;
}

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Output:

10 occurs 2 times
20 occurs 1 times
13 occurs 0 times
30 occurs 2 times

Program 2:

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// C++ program to illustrate the
// unordered_multimap::count()
#include <bits/stdc++.h>
using namespace std;
  
int main()
{
  
    // declaration
    unordered_multimap<char, char> sample;
  
    // inserts key and element
    sample.insert({ 'a', 'b' });
    sample.insert({ 'a', 'b' });
    sample.insert({ 'b', 'c' });
    sample.insert({ 'r', 'a' });
    sample.insert({ 'r', 'b' });
  
    cout << "a occurs " << sample.count('a'
         << " times";
  
    cout << "\nb occurs " << sample.count('b'
         << " times";
  
    cout << "\nz occurs " << sample.count('z'
         << " times";
  
    cout << "\nr occurs " << sample.count('r'
         << " times";
  
    return 0;
}

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Output:

a occurs 2 times
b occurs 1 times
z occurs 0 times
r occurs 2 times


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