5. Hashing Implementation with C++ STL

In C++, instead of creating a Hash Table manually, you could use Standard Template Library (STL). The STL implementation automatically handles hash functions, collisions, and rehashing when the load factor gets too high.

5.1. std::unordered_map (Key-Value)

std::unordered_map is a Hash Map implementation for Key-Value pairs. The purpose of this template is to map Keys to Values. It acts like a dictionary, where you look up a word (key) to get its definition (value).

#include <iostream>
#include <string>
#include <unordered_map>

int main() {
    // Key: string (name), Value: int (grade)
    std::unordered_map<std::string, int> studentGrades;

    studentGrades["Budi"] = 90;
    studentGrades["Ani"] = 85;

    // Access value using key
    std::cout << "Budi's Grade: " << studentGrades["Budi"] << std::endl;
}

5.2. std::unordered_set (Unique Keys)

std::unordered_set is a Hash Set implementation that only stores unique keys. This template is used to check whether a key is on the list or not, like a guest book.

#include <iostream>
#include <string>
#include <unordered_set>

int main() {
    std::unordered_set<std::string> attendanceList;

    attendanceList.insert("Budi");
    attendanceList.insert("Ani");
    attendanceList.insert("Budi"); // Ignored, because "Budi" already exists

    // Check existence
    if (attendanceList.count("Budi") > 0) {
        std::cout << "Budi is present." << std::endl;
    }
}

5.3. Comparison: map vs. set