Summary  
This chapter demonstrates how to use associative containers to store, access, and manipulate key-value and unique-key collections efficiently, covering insertion, lookup, removal, iteration, and performance considerations.

General domain of usage  
Word frequency analysis


#define CATCH_CONFIG_MAIN
#include <catch2/catch.hpp>


#include <string>
#include <unordered_set>

std::string remove_duplicates(const std::string& input);

TEST_CASE("remove_duplicates removes duplicates and preserves order", "[remove_duplicates]") {
    REQUIRE(remove_duplicates("banana") == "ban");
    REQUIRE(remove_duplicates("apple") == "aple");
    REQUIRE(remove_duplicates("aabbcc") == "abc");
    REQUIRE(remove_duplicates("") == "");
    REQUIRE(remove_duplicates("abcdef") == "abcdef");
    REQUIRE(remove_duplicates("aabacadae") == "abcde");
}

TEST_CASE("remove_duplicates keeps first occurrence only", "[remove_duplicates]") {
    REQUIRE(remove_duplicates("mississippi") == "misp");
    REQUIRE(remove_duplicates("testcase") == "tesca");
}

test.cpp

Master modern C++ through the power of the Standard Template Library. Learn how containers, iterators, and algorithms work together to create clean, efficient, and expressive code. Explore essential containers like vector, map, and unordered_map, understand their performance trade-offs, and apply core algorithms for searching, sorting, transforming, and generating data. Build a solid foundation for writing robust, reusable, and high-performance C++ programs.

Overview of the STL, its design philosophy, and how containers and algorithms interact to provide powerful abstractions in C++.

Deep dive into the most important STL containers, their strengths, weaknesses, and advanced usage patterns.

Master the use of STL algorithms, from basic to advanced, and learn how to leverage them for expressive and efficient code.

Challenge: Associative Containers in Action

解答