Unordered Map Iterator C

Introduction

In C++, the unordered_map container is used to store key-value pairs in an unordered manner. It is a part of the Standard Template Library (STL) and is widely used in various applications. The unordered_map iterator is used to traverse the elements of an unordered_map container. In this article, we will discuss the basics of the unordered_map iterator in C++.

What is an Iterator?

Before we dive into the details of the unordered_map iterator, let’s understand what an iterator is. In C++, an iterator is an object that points to an element in a container. It allows us to access and manipulate the elements of a container.

The Unordered_Map Iterator

The unordered_map iterator is used to traverse the elements of an unordered_map container. It is a bidirectional iterator, which means we can move forward and backward through the elements. There are two types of iterators in an unordered_map container: 1. const_iterator: This iterator is used when we want to read the elements of the container. 2. iterator: This iterator is used when we want to modify the elements of the container.

Using the Unordered_Map Iterator

To use the unordered_map iterator, we need to declare an iterator object. The syntax for declaring an iterator is as follows: “`c++ unordered_map myMap; unordered_map::iterator itr; “` In the above code, we have declared an unordered_map container named myMap that stores key-value pairs of integer and string data types. We have also declared an iterator object named itr that will be used to traverse the elements of myMap.

Traversing the Elements

To traverse the elements of an unordered_map container, we can use a for loop or a while loop. The syntax for traversing an unordered_map container using a for loop is as follows: “`c++ for(itr = myMap.begin(); itr != myMap.end(); ++itr) { cout << "Key: " << itr->first << " Value: " << itr->second << endl; } ``` In the above code, we have used a for loop to traverse the elements of myMap. The begin() function returns the iterator to the first element of the container, while the end() function returns the iterator to the last element of the container. The -> operator is used to access the key-value pairs of the current element.

Modifying the Elements

To modify the elements of an unordered_map container, we can use the iterator object along with the -> operator. The syntax for modifying an element is as follows: “`c++ itr->second =”New Value”; “` In the above code, we have modified the value of the current element using the iterator object itr and the -> operator.

Conclusion

In this article, we have discussed the basics of the unordered_map iterator in C++. We have learned how to declare an iterator object, traverse the elements of a container, and modify the elements of a container using the iterator object. The unordered_map iterator is a powerful tool that can make our programming tasks much easier. We hope this article has provided a good understanding of the unordered_map iterator and its usage in C++.