What are some examples of using C++ maps?

Can you give me some examples of how to use maps in C++?

Sure! In C++, a map is a collection of key-value pairs. For example, you can create a map to store the ages of people like this:

#include <map>
#include <string>

std::map<std::string, int> ages;
ages["Alice"] = 30;
ages["Bob"] = 25;

This creates a map where the keys are names and the values are ages.

How do I iterate over a map in C++?

You can iterate over a map using a for loop like this:

for (const auto& pair : ages) {
    std::cout << pair.first << " is " << pair.second << " years old." << std::endl;
}

This will print each name and age in the map.

What happens if I try to access a key that doesn't exist?

If you try to access a key that doesn't exist, it will create a new entry with that key and a default value. For example:

int value = ages["Charlie"]; // Charlie doesn't exist, so this creates an entry with value 0.

You can also use the find method to check if a key exists before accessing it.

Can I use custom objects as keys in a C++ map?

Yes, you can use custom objects as keys in a C++ map, but you need to define a comparison operator for your object. For example:

struct Point {
    int x, y;
    bool operator<(const Point& other) const {
        return (x < other.x) || (x == other.x && y < other.y);
    }
};

std::map<Point, std::string> pointMap;

This allows you to use Point objects as keys.