Sorting C++ unordered_map: Simple Guide

In C++, hash tables are unordered data structures, so they cannot be sorted directly. If sorting elements within a hash table is necessary, you can copy the elements to a new container (such as a vector) and then sort that container.

Here is a sample code demonstrating how to copy elements from a hash map to a vector and sort them.

#include <iostream>
#include <unordered_map>
#include <vector>
#include <algorithm>

int main() {
    std::unordered_map<int, std::string> hashTable = {
        {1, "apple"},
        {3, "banana"},
        {2, "orange"}
    };

    std::vector<std::pair<int, std::string>> vec(hashTable.begin(), hashTable.end());

    // 对vector中的元素进行排序
    std::sort(vec.begin(), vec.end(), [](const std::pair<int, std::string>& a, const std::pair<int, std::string>& b) {
        return a.first < b.first;
    });

    // 打印排序后的结果
    for (const auto& pair : vec) {
        std::cout << pair.first << ": " << pair.second << std::endl;
    }

    return 0;
}

In the example above, the elements in the hash table are first copied to a vector, then the elements in the vector are sorted using the std::sort function, and finally the sorted results are printed.