Empty()-This function returns a Boolean value denoting whether a map is empty. The value_datatype denotes the datatype of the values corresponding to the map keys. In the above example, erase function is used to erase the element with the given range i.e begin to end. It returns an iterator that points to the next element of the deleted element or returns the number of deleted elements.
C++ Map also contains various member functions that will be discussed in this section. Functions of the map in C++ to create our key-value pairs. To work with C++ map, we create an iterator to iterate over the elements. We can use the erase() function to delete a value from a map. We simply create an iterator that points to the element to be deleted. The iterator is then passed to the erase() function.
You learned the syntax of maps, along with their parameters, and their uses in-depth. This article dived deep into how you can create a map and all the member functions of the map. This function swaps the elements of two maps of the same type. This function returns a pointer pointing corresponding to the key or will point before the key value. This function returns a pointer pointing corresponding to the key or will point after the key value.
For example to access element of a particular position ,you have to iterate from a known position to that particular position. The way we use normal parameters to pass as a value to function, in the same manner template parameters can be used to pass type as argument to function. Basically, solanadata plus it tells what type of data is being passed to the function. End()– returns an iterator to the theoretical element after the last element. Map only stores unique keys which eliminates redundancy of data. Erase – it removes the element which is specified at a location by the iterator.
Equal_range() is a built-in function in C++ STL which returns an iterator of pairs. The pair refers to the bounds of a range that includes all the elements in the container which have a key equivalent to k. In any case, the map container class of the C++ STL supports an “associative” container in which unique keys are “mapped” to their corresponding values. These key/value pairs are, in fact, kept in STL pair structs which we refer to as the “elements” or “items” of the map. Maps are containers which store elements by mapping their value against a particular key. It stores the combination of key value and mapped value following a specific order.
In the above example, we have used the erase() method to remove an element from the unordered map. Here, we have first created an unordered map named unordered_map_1. Then, we created another unordered map called unordered_map_2 by copying all the elements of unordered_map_1. A value is stored by applying hash function on a key. So, values are not stored in sorted order. The erase_if method deletes all elements for which the given predicate returns true.
To access the elements we use keywords, first and second to access the first and second element respectively. After creating the generic function, compiler will automatically generate correct code for the type of data used while executing the function. We have a problem accessing every element in the map because the map has no index so that is why we have the concept of an iterator. In this section, we will know how to initialize the map.
As we know the map store key-value pairs. Map is an associative container/array that store the elements as a combination of key-value pairs . This function returns a constant pointer pointing to the element that comes after the last element. This function returns a constant pointer pointing to the first element. This function returns a constant pointer pointing to the element that comes before the first element.