2 Ways to Sort Map by Values in C++

We simply create an iterator that points to the element to be deleted. The iterator is then passed to the erase() function. Empty()-This function returns a Boolean value denoting whether a map is empty.

Using the insert_or_assign() function to insert or modify an existing entry. Since the key 1 already exists, its value will be changed to 6. Include the iostream header file into our code to use its functions. Insert- with this variation, the entries will be inserted within the range defined by start_itr and end_itr from another map.

Before we move on to what iterators are there in the map class let us have a recap of what iterators are in C++. Functions, that perform different map operations. We shall look into them one by one and try to understand how they work through examples.

Mm insert() – To insert elements in the multimap container. We can use the priority queue and own comparator function to sort the map. Before reading this article please go through our article on how to define your comparator for priority queue in C++ STL. A map in C++ STL is normally sorted based on its keys. But there may be instances when we require to sort the map based on the values. In this article, we are going to discuss how to sort a map based on the values instead of keys.

Now what if want to display items of a map in sorted order of keys. For example for above map we want to display the items in descending order of frequency count i.e. Internally, the elements in a map are always sorted by its key following a specific strict weak ordering criterion indicated by its internal comparison object . After storing unique array elements with its frequency in Map, each unique element is restored in the given array, frequency no.of times as per the order of Map.

This function returns a pointer pointing to the last element of the container. This function returns a pointer pointing to the element that comes before the first element of the container. End() function returns a pointer pointing to the element that comes after does pubg new state have controller support the last element of the container. This element is not real, it is a virtual element that contains the address of the last element. Begin() is a member function of C++ Map in STL. Begin() function returns a pointer pointing to the first element of the container.

Maps are typically implemented as binary search trees. Check the below code to see the detailed implementation and output to see the sorted map. Extra memory is allocated only for unique array elements. The iterators itB and itE were dereferenced to have their elements, with the indirection operator. Although we cannot directly have elements sorted with respect to values, there are some indirect ways using which we can sort a Map by values in C++. Or alternatively, just copy the values from the map, leaving the keys, and sort the resulting vector directly.

Use the size() function to get the size of the map named Students. Insert values into the map Students. A key of 201 and a value of John will be inserted into the map. A key of 200 and a value of Alice will be inserted into the map.

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