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Efficiently Sort Your Maps: A Beginner’s Guide in C++

Title: Sorting a Map in C++ – An Informative Guide for BeginnersSorting maps in C++ can be a daunting task for beginners. However, it is an essential technique to master as it can make your code more efficient and organized.

In this guide, we will be discussing two popular methods of sorting maps – using std::vector and std::sort algorithm and using std::map and std::map::emplace. We will break down each method into simple steps for beginners to follow and provide code examples to illustrate each step.

Sorting a Map by Value Using std::vector and std::sort Algorithm in C++

The first method we will be discussing is using std::vector and std::sort algorithm. Let’s start with a brief explanation of what std::map is.

A std::map is a type of associative container that stores elements in a key-value format. Each element has a unique key that relates to its value.

Now, let’s delve into the steps for sorting a map by value using std::vector and std::sort algorithm:

Step 1: Create a std::map object with integer strings as keys and regular strings as values

We start by creating a std::map object with key-value pairs. Here is an example:

std::map myMap;

myMap = { {“banana”, 60}, {“apple”, 50}, {“orange”, 70} };

Step 2: Initialize a vector container to store the map pairs using emplace_back method

Next, we create a vector container to store the key-value pairs of the map.

Here is an example:

std::vector> vecContainer;

for (auto& it : myMap)

{

vecContainer.emplace_back(it);

}

Step 3: Sorting the vector using std::sort algorithm and lambda expression

Now, we sort the vector based on the values of the map. Here is an example:

std::sort(vecContainer.begin(), vecContainer.end(),

[](const std::pair& a, const std::pair& b)

{ return a.second < b.second; });

Step 4: Outputting the sorted vector elements as a map representation

Finally, we output the sorted vector elements as a map representation.

Here is an example:

for (auto& it : vecContainer)

{

std::cout << it.first << " " << it.second << std::endl;

}

Sorting a Map by Value Using std::map and std::map::emplace in C++

The second method we will be discussing is using std::map and std::map::emplace. This method is slightly more complex than the first method but is more efficient.

Here are the steps to follow:

Step 1: Creating a std::map object with integer strings as keys and regular strings as values

We start by creating a std::map object with key-value pairs. Here is an example:

std::map myMap;

myMap = { {“banana”, 60}, {“apple”, 50}, {“orange”, 70} };

Step 2: Initializing a second map object to store the value-sorted elements using emplace method and reversed key-value pairs

Next, we create a second map object to store the sorted elements.

Here is an example:

std::map sortedMap;

for (auto& it : myMap)

{

sortedMap.emplace(std::make_pair(it.second, it.first));

}

Step 3: Sorting the second map by keys, which contain the values of the first map

We sort the second map by keys which contain the values of the first map. Here is an example:

for (auto& it : sortedMap)

{

std::cout << it.second << " " << it.first << std::endl;

}

Conclusion:

Sorting maps in C++ can seem daunting at first, but with practice, it becomes more natural.

The two methods discussed in this guide – using std::vector and std::sort algorithm and using std::map and std::map::emplace – are efficient and straightforward. By following the simple steps outlined in each method, you can easily sort your maps by value.

Sorting maps is an essential task in C++ programming that can make code more efficient and organized. This article discussed two popular methods of sorting maps – using std::vector and std::sort algorithm and using std::map and std::map::emplace.

By following the simple steps outlined in each method, beginners can easily sort their maps by value. Mastering these methods can vastly improve your programming skills, so keep practicing to become more proficient.

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