C++ Map

The C++ map is an associative container that stores elements in key-value pairs, where each key is unique within the map and maps to a corresponding value.

For Example:A map of student where Student ID is the key and name is the value can be represented as:

Here is an example of how to create a map of student

  // Create a map to store <student ID, name>
  std::map<int, std::string> student;

Insert the student’s name into the student Map

  // Insert some sample data
  student[6] = "John";
  student[7] = "Sarah";
  student[8] = "Mark";

Iterating over a map and printing its contents

  // Iterate and print the map
  std::cout << "Students:" << std::endl;
  for(auto it = student.begin(); it != student.end(); ++it)
 {
    std::cout << it->first << " => " << it->second << std::endl; 
  }

The auto keyword in C++ is used to automatically deduce the type of a variable from its initializer. Here are some examples of using auto:

// The type of 'i' is deduced to be int
auto i = 5; 

// The type of 'd' is deduced to be double
auto d = 3.14;

// The type of 's' is deduced to be std::string
auto s = "Hello";

Here are a few different ways to delete a key-value pair from a C++ map:

1. Use map.erase()

std::map<int, std::string> student;
student.erase(3); // erases element with key 3

2. Use the iterator returned by find()

std::map<int, std::string> student;
auto it = student.find(5); 

if (it != student.end())
{
  student.erase(it);
}

3. Assign NULL to the key

std::map<int, std::string> student;
student[2] = NULL; // erases key 2

4. Reassign the key

std::map<int, std::string> student;
student[4] = "New Value"; // erases previous value for key 4

5. Clear the entire map

std::map<int, std::string> student;
student.clear(); // removes all elements

So in summary, to delete a single key, use student.erase(), find() + erase(), assign NULL or reassign the key.To delete all keys, call student.clear().

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