1. Introduction to C++: A Comprehensive Guide with Code Examples - 2023 2. Mastering Data Types in C++: A Comprehensive Guide with Codes and Examples (2023) 3. Learn About Variables and Types of Variables in C++ | Codzify.com 4. Control Statements in C++: A Comprehensive Guide for 2023 5. C++ Tutorial: Understanding Switch Statements with Codes and Examples in 2023 6. Understanding Memory Allocation and Pointers in C++: A Beginners Guide 7. Functions in C++ 8. Call by value and Call by Reference in C++ in depth 9. Array in C++ 10. 2d arrays in C++ 11. Classes and Objects in C++ 12. Static Functions in C++ 13. Constructors and Destructors in C++ - A Complete Guide with Examples 14. Mastering Copy Constructor in C++ - Shallow vs Deep Copy with Examples | Codzify 15. Understanding Friend Functions in C++ Made Simple! 16. Inline Functions in C++ 17. this Pointer in C++ 18. Mastering Inheritance in C++: Types and Examples Explained 19. Types of Inheritance in C++ 20. Polymorphism in C++ Explained with Codes and Examples in 2023 21. Templates in C++ 22. Getting the Value of a MultiMap in C++: Step-by-Step Guide with Examples 23. Multimap Find and Replace Operator in C++: Step-by-Step Guide - Codzify Topics 24. Exploring the Next_Permutation Algorithm without STL in C++ - Codzify Topics 25. C++ - The Difference Between Map and HashMap in STL 26. Updating Values in a std::multimap in C++ - Codzify Topics 27. Which data structure sorts the elements on insertion in C++ STL? 28. Can we implement Red Black Tree in c++ by STL containers? 29. How to Dynamically Declare an Array of Objects with a Constructor in C++ - A Step-by-Step Guide 30. What is the difference between a pointer and an object in C++? 31. Mastering Red-Black Trees with STLs Internal Implementation: A Step-by-Step Guide

Getting the value of a multimap in C++

Article by: Manish Methani

Last Updated: September 9, 2021 at 8:04am IST
6 min 53 sec

Table of Contents:

A MultiMap is a versatile data structure in C++ that allows you to store and manage key-value pairs where a key can have multiple associated values. Accessing and retrieving the values associated with a specific key in a MultiMap is a common operation. In this step-by-step guide, we'll walk you through how to get the values of a MultiMap in C++ with code examples.

Step 1: Include the Necessary Headers

First, you need to include the necessary C++ Standard Library headers to work with MultiMaps. You'll need #include <iostream>, which is standard for input and output, and #include <map>, which is used for MultiMap functionality.

#include <iostream>
#include <map>

Step 2: Create a MultiMap

Next, you need to create a MultiMap. You can define a MultiMap with a specific key and associated values. Here's an example:

std::multimap<std::string, int> myMultiMap;

In this example, we've created a MultiMap where the key is a string and the associated values are integers.

Step 3: Insert Key-Value Pairs

Now, let's insert key-value pairs into the MultiMap. You can use the insert method to add entries.

myMultiMap.insert(std::make_pair("apple", 5));
myMultiMap.insert(std::make_pair("banana", 3));
myMultiMap.insert(std::make_pair("apple", 8));
myMultiMap.insert(std::make_pair("cherry", 10));
myMultiMap.insert(std::make_pair("banana", 2));

Step 4: Get Values Associated with a Key

To retrieve the values associated with a specific key in the MultiMap, you can use the equal_range method. This method returns a pair of iterators representing the range of elements with the specified key. You can then iterate through this range to access the associated values.

std::string keyToSearch = "apple";
auto range = myMultiMap.equal_range(keyToSearch);

for (auto it = range.first; it != range.second; ++it) {
    std::cout << keyToSearch << " has value: " << it->second << std::endl;
}

In this example, we search for the key "apple" and iterate through the range of values associated with it. The output will display the associated values.

Step 5: Full Example Code

Here's the complete example code:

#include <iostream>
#include <map>

int main() {
    std::multimap<std::string, int> myMultiMap;
    
    myMultiMap.insert(std::make_pair("apple", 5));
    myMultiMap.insert(std::make_pair("banana", 3));
    myMultiMap.insert(std::make_pair("apple", 8));
    myMultiMap.insert(std::make_pair("cherry", 10));
    myMultiMap.insert(std::make_pair("banana", 2));

    std::string keyToSearch = "apple";
    auto range = myMultiMap.equal_range(keyToSearch);

    for (auto it = range.first; it != range.second; ++it) {
        std::cout << keyToSearch << " has value: " << it->second << std::endl;
    }

    return 0;
}

Output:

apple has value: 5
apple has value: 8

When you run this code, it will display the values associated with the key "apple" in the MultiMap.

Using a MultiMap in C++ allows you to efficiently manage multiple values associated with a key. You can easily retrieve these values using the equal_range method, as demonstrated in this step-by-step guide.

FAQ

1. How can I find and replace in a C++ multimap?

To find and replace in a C++ multimap, you need to:

  1. Iterate through the multimap using iterators.
  2. Search for the key you want to replace.
  3. If found, update the associated values with the new values.
  4. Repeat this process for all occurrences of the key if necessary.

2. Why does std::unordered_map provide an equal_range member function?

`std::unordered_map` provides an `equal_range` member function to efficiently find a range of elements with the same key. This function is useful for operations like counting the number of elements with a specific key, iterating over all elements with the same key, or searching for a specific range of elements.

3. Does a C++ multimap preserve the insert order for multiple values mapped to the same key?

Yes, a C++ multimap preserves the insert order for multiple values mapped to the same key. The multimap allows duplicate keys and maintains the order of insertion. When you iterate through the multimap, the elements are presented in the order they were added.

4. How can you find the total number of values for a particular key in a Multimap in C++?

To find the total number of values for a particular key in a Multimap in C++, you can:

  1. Use the `count` member function to count the occurrences of a specific key.
  2. Iterate through the Multimap and manually count the values associated with the key.
  3. Use the `equal_range` function to find a range of elements with the same key and calculate the count.

5. How can you add multiple elements of pairs in a multimap in C++ using the insert() function?

To add multiple elements of pairs in a multimap in C++ using the `insert()` function:

  1. Create a pair or pairs of key-value entries.
  2. Use the `insert()` function with the pairs to add them to the multimap.
  3. Repeat the process for multiple pairs, and they will be inserted into the multimap.

Learn Flutter, FlutterFlow,
Firebase & Angular.

Looking to learn how to create the production-ready apps
from scratch? Well, you are at the right place.

₹1299 or $15.56

Learn to create the Dating App using No-Code Tool FlutterFlow

Level: Advanced

Explore Curriculum
₹1299 or $15.56

Flutter Mobile App Development Course

Explore Curriculum
₹1299 or $15.56

The Complete Angular Course

Explore Curriculum
₹1299 or $15.56

Dart Programming for Absolute Beginners

Coming Soon
FREE

Next.js course

Start Watching
FREE

Fundamentals of Computer Programming Languages

Start Watching
FREE

Learn HTML, CSS & Bootstrap

Start Watching

Latest Web Stories

1

Learn how to open WhatsApp using FlutterFlow | Step by Step Guide

Test your skills with these expert-led curated
Mock Tests.

C Programming Test

Test your C Programming skills with this comprehensive mock test on C Programming.

Take Test

Flutter Test

Solve most asked Interview Questions on Flutter and Test your foundational skills in flutter.

Take Test

GATE(CSE) Operating Systems

Solve most asked GATE Questions in Operating Systems and test your Gate Score.

Take Test

HTML,CSS Test

This is a mock test designed to help you assess your knowledge and skills in HTML and CSS.

Take Test

(GATE CSE) Data Structures & Algorithms Test

Solve most asked GATE Questions in Data Structures and Algorithms and test your Gate Score.

Take Test

Download the Codzify
Mobile App


Learn Anytime, Anywhere at your own pace. Scan the QR Code with your Mobile Camera to Download the Codzify Mobile App.

Codzify Mobile App Codzify Mobile App
Codzify Logo

Terms and Conditions    Cookie Policy   Refund Policy   Adsense Disclaimer