推力:并行计算多个段的set_difference

#include <iostream>
#include <vector>
#include <algorithm>
#include <thread>
#include <mutex>

std::mutex mtx;

void parallel_set_difference(const std::vector<int>& A, const std::vector<int>& B, std::vector<int>& result, int start, int end) {
    std::vector<int> temp;
    std::set_difference(A.begin() + start, A.begin() + end, B.begin(), B.end(), std::back_inserter(temp));
    
    std::lock_guard<std::mutex> lock(mtx);
    result.insert(result.end(), temp.begin(), temp.end());
}

int main() {
    std::vector<int> A = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10};
    std::vector<int> B = {5, 6, 7, 8, 9, 10};
    std::vector<int> result;

    int num_threads = 4;
    int chunk_size = A.size() / num_threads;

    std::vector<std::thread> threads;
    for (int i = 0; i < num_threads; ++i) {
        int start = i * chunk_size;
        int end = (i == num_threads - 1) ? A.size() : start + chunk_size;
        threads.emplace_back(parallel_set_difference, std::ref(A), std::ref(B), std::ref(result), start, end);
    }

    for (auto& thread : threads) {
        thread.join();
    }

    std::sort(result.begin(), result.end());
    for (const auto& elem : result) {
        std::cout << elem << " ";
    }

    return 0;
}