Last Updated : 28 Dec, 2022
The unordered_multimap::count() is a built-in function in C++ STL that 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 that 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.
Time Complexity: O(N)
Below programs illustrates the above function: Program 1:
CPP
// 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;
}
Output:
10 occurs 2 times 20 occurs 1 times 13 occurs 0 times 30 occurs 2 times
Program 2:
CPP
// 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;
}
Output:
a occurs 2 times b occurs 1 times z occurs 0 times r occurs 2 times
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