map Add in C++

In C++, we can use the unordered_map STL (standard template library) container to store elements in a hash table. To add an element to a hash table using an unordered_map container, follow the steps below:

Step 1: Create an empty unordered_map container.

unordered_map umap;

This statement creates an empty hash table named umap that maps string keys to integer values.

Step 2: Insert key-value pairs into the unordered_map container using the insert() function.

umap.insert(make_pair("apple", 10));

This statement inserts a new key-value pair "apple"->10 into the hash table.

Alternatively, we can also use the square bracket notation to add a new element. If the key exists in the hash table, its value will be updated; otherwise, a new key-value pair will be added to the hash table.

umap["banana"] = 5;

This statement adds a new key-value pair "banana"->5 into the hash table.

Below is the complete example code:

#include 
#include 
using namespace std;
int main()

{

    // Create an empty hash table

    unordered_map umap;
// Insert keys and values into the hash table

    umap.insert(make_pair("apple", 10));

    umap["banana"] = 5;
// Print the size and contents of the hash table

    cout << "Size of umap: " << umap.size() << endl;

    for (auto itr = umap.begin(); itr != umap.end(); itr++) {

        cout << itr->first << " : " << itr->second << endl;

    }
return 0;

}

Output:

Size of umap: 2
apple : 10
banana : 5