问C++如何从类似JSON的文本文件中获取特定的值？

EN

#include <iostream>
#include <fstream>
#include <string>
#include <regex>
#include <unordered_map>
#include <utility>
#include <map>

// ------------------------------------------------------------
// Create aliases. Save typing work and make code more readable
using Pair = std::pair<std::string, unsigned int>;
// Standard approach for counter
//using Counter = std::unordered_map<Pair::first_type, Pair::second_type>;
using Counter = std::map<Pair::first_type, Pair::second_type>;
// Sorted values will be stored in a vector
using Top = std::vector<Pair>;
// ------------------------------------------------------------

// Regexes
const std::regex unigramLineIdentifierRegex{R"(\"unigramCount\":\{(.*)\})"};
const std::regex unigramCountRegex{ R"((\"[a-zA-Z ,]+\"\:\d+)+)" };
const std::regex wordAndCountRegex(R"(\"([a-zA-Z ,]+)\":(\d+))");

int main() {
    // Open the file and check, if it could be opened
    if (std::ifstream ifs{"text.txt"}; ifs) {

        // Read the complete textfile into a string
        std::string text(std::istreambuf_iterator<char>(ifs), {});
        
        // Here we will count the words
        Counter counter{};

        // Now extract all lines containing the unigram line pattern into a std::vector
        std::vector unigramLine(std::sregex_token_iterator(text.begin(), text.end(), unigramLineIdentifierRegex), {});

        // For each of the found lines containg a unigram record
        for (const std::string& wordAndCount : unigramLine) {

            // Extract all word count pairs
            std::vector unigrams(std::sregex_token_iterator(wordAndCount.begin(), wordAndCount.end(), unigramCountRegex), {});

            // Go over all word/count strings and split them up
            for (const std::string unigram : unigrams) {

                // Find the word part and the count part
                std::smatch smWordAndCount{};
                if (std::regex_match(unigram, smWordAndCount, wordAndCountRegex)) {

                    // Increment the global counter
                    counter[smWordAndCount[1]] += std::stoi(smWordAndCount[2]);
                }
            }
        }
        // Here we will store the top 3
        Top top(3);

        // Copy and sort. Get only the biggest 3
        std::partial_sort_copy(counter.begin(), counter.end(), top.begin(), top.end(), [](const Pair& p1, const Pair& p2) { return p1.second > p2.second; });

        // Debug output. Show the result´, the top3 on the screen
        for (const auto& [word, count] : top)
            std::cout << word << " \t--> " << count << '\n';
    }
    else std::cerr << "\n*** Error: Could not open source file\n\n";
}