How is the std map used in C++?

In C++, std::map is an associative container that stores a collection of key-value pairs in a sorted manner. It is implemented based on a red-black tree, providing efficient operations for searching, inserting, and deleting elements.

When using std::map, you need to include the header file. The syntax for creating a map object is as follows:

std::map<Key, Value> mapName;

Key represents the type of key, Value represents the type of value, and mapName is the name of the map object.

You can insert key-value pairs into a map using the insert() function.

mapName.insert(std::pair<Key, Value>(key, value));

You can also use the subscript operator [] to insert key-value pairs:

mapName[key] = value;

You can use the find() function to search for the value of a specified key:

std::map<Key, Value>::iterator it = mapName.find(key);
if (it != mapName.end()) {
    // 键存在，可以通过it->second访问对应的值
} else {
    // 键不存在
}

You can use the erase() function to delete key-value pairs of a specific key.

mapName.erase(key);

You can use the clear() function to remove all key-value pairs from a map.

mapName.clear();

You can traverse the entire map using an iterator.

for (std::map<Key, Value>::iterator it = mapName.begin(); it != mapName.end(); ++it) {
    // 可以通过it->first访问键，通过it->second访问值
}

It is important to note that in std::map, keys are unique, and if you insert a duplicate key, it will overwrite the original value. If you need to store key-value pairs with duplicate keys, you can use std::multimap.