unordered_multimap size() function in C++ STL

The unordered_multimap::size() is a built-in function in C++ STL which returns the size of the unordered_multimap. It denotes the number of elements in that container. Syntax:

unordered_multimap_name.size()

Parameters: The function does not accept any parameters. Return Value: It returns an integral values which denotes the size of the containers. Below programs illustrates the above function: Program 1:

CPP

// C++ program to illustrate the
// unordered_multimap::size()
#include <bits/stdc++.h>
using namespace std;

int main()
{

    // declaration
    unordered_multimap<int, int> sample1, sample2;

    // inserts key and element
    // in sample1
    sample1.insert({ 10, 100 });
    sample1.insert({ 50, 500 });

    // inserts key and element
    // in sample1
    sample2.insert({ 20, 200 });
    sample2.insert({ 30, 300 });
    sample2.insert({ 30, 150 });

    cout << "The size of Sample1 is: " << sample1.size();

    cout << "\nKey and Elements of Sample1 are:";
    for (auto it = sample1.begin(); it != sample1.end(); it++) {
        cout << "{" << it->first << ", " << it->second << "} ";
    }

    cout << "\n\nThe size of Sample2 is: " << sample2.size();

    cout << "\nKey and Elements of Sample2 are:";
    for (auto it = sample2.begin(); it != sample2.end(); it++) {
        cout << "{" << it->first << ", " << it->second << "} ";
    }

    return 0;
}

Output:

The size of Sample1 is: 2
Key and Elements of Sample1 are:{50, 500} {10, 100} 

The size of Sample2 is: 3
Key and Elements of Sample2 are:{20, 200} {30, 150} {30, 300}

Program 2:

CPP

// C++ program to illustrate the
// unordered_multimap::size()
#include <bits/stdc++.h>
using namespace std;

int main()
{

    // declaration
    unordered_multimap<char, char> sample1, sample2;

    // inserts key and element
    // in sample1
    sample1.insert({ 'a', 'A' });
    sample1.insert({ 'g', 'G' });

    // inserts key and element
    // in sample1
    sample2.insert({ 'b', 'B' });
    sample2.insert({ 'c', 'C' });
    sample2.insert({ 'd', 'D' });

    cout << "The size of Sample1 is: " << sample1.size();

    cout << "\nKey and Elements of Sample1 are:";
    for (auto it = sample1.begin(); it != sample1.end(); it++) {
        cout << "{" << it->first << ", " << it->second << "} ";
    }

    cout << "\n\nThe size of Sample2 is: " << sample2.size();

    cout << "\nKey and Elements of Sample2 are:";
    for (auto it = sample2.begin(); it != sample2.end(); it++) {
        cout << "{" << it->first << ", " << it->second << "} ";
    }

    return 0;
}

Output:

The size of Sample1 is: 2
Key and Elements of Sample1 are:{g, G} {a, A} 

The size of Sample2 is: 3
Key and Elements of Sample2 are:{d, D} {b, B} {c, C}

unordered_multimap size() function in C++ STL

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