<map> is an ordered associative container: a sorted tree of key-value pairs with O(log n) insertion, deletion, and lookup. It maintains keys in sorted order and allows iteration from min to max.

Use std::unordered_map if you don't need order; use std::map if you do or if you need to iterate a range of keys.

This example builds a map of names to ages, iterates through in sorted order, and looks up a specific key.

// compile: g++ -std=c++11 -o mapexample mapexample.cpp
// run: ./mapexample
// description: map insertion and lookup
 
#include <map>
#include <iostream>
#include <string>
 
int main() {
    std::map<std::string, int> age;
    age["alice"] = 30;
    age["bob"] = 25;
    age["charlie"] = 35;
 
    for (const auto& [name, years] : age) {
        std::cout << name << ": " << years << "\n";
    }
 
    std::cout << "alice is " << age["alice"] << "\n";
 
    return 0;
}