给定n个正整数numbers.Print在C++上此数组中有多少个数字至少出现2次

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

int countDuplicates(const std::vector<int>& numbers) {
    std::unordered_map<int, int> countMap;
    for (int num : numbers) {
        countMap[num]++;
    }
    
    int duplicates = 0;
    for (const auto& pair : countMap) {
        if (pair.second >= 2) {
            duplicates++;
        }
    }
    
    return duplicates;
}

int main() {
    std::vector<int> numbers = {1, 2, 3, 2, 4, 3, 5, 6, 7, 8, 8};
    int result = countDuplicates(numbers);
    std::cout << "Number of duplicates: " << result << std::endl;
    return 0;
}