#include #include #include #include struct Purchase { std::string date; std::string product; double price; }; bool compareDates(const Purchase& p1, const Purchase& p2) { return p1.date

要修改代码以比较月日距离现在的远近，您需要使用日期时间库（如<chrono>）和当前日期时间进行比较。下面是修改后的代码示例：

#include <iostream>
#include <string>
#include <vector>
#include <algorithm>
#include <chrono>
struct Purchase {
    std::string date;
    std::string product;
    double price;
};
// 比较两个日期之间的天数差距
int compareDates(const std::string& date1, const std::string& date2) {
    // 解析日期字符串为std::tm结构体
    std::tm tm1 = {};
    strptime(date1.c_str(), "%Y-%m-%d", &tm1);
    
    std::tm tm2 = {};
    strptime(date2.c_str(), "%Y-%m-%d", &tm2);
    // 将std::tm转换为std::chrono::system_clock时间点
    auto timePoint1 = std::chrono::system_clock::from_time_t(std::mktime(&tm1));
    auto timePoint2 = std::chrono::system_clock::from_time_t(std::mktime(&tm2));
    // 计算时间点之间的天数差距
    auto duration = timePoint1 - timePoint2;
    return duration / (std::chrono::hours(24));
}
bool compareDatesWithCurrent(const Purchase& p) {
    // 获取当前日期时间
    auto nowTimePoint = std::chrono::system_clock::now();
    
	// 转换为当地时间结构体
	time_t nowTimeT = std :: chrono :: system_clock :: to_time_t(nowTimePoint);
	std :: tm now = * localtime( & nowTimeT);
	now.tm_year += 1900; // 年份要加上1900
	now.tm_mon += 1; // 月份要加1
    
    return compareDates(p.date, std::to_string(now.tm_year) + "-" + std::to_string(now.tm_mon) + "-" + std::to_string(now.tm_mday)) > 0;
}
double calculateAveragePrice(const std::vector<Purchase>& purchases, const std::string& product, int N) {
    double sum = 0.0;
    int count = 0;
    for (const Purchase& purchase : purchases) {
        if (purchase.product == product && compareDatesWithCurrent(purchase)) {
            sum += purchase.price;
            count++;
            if (count == N) break;
        }
    }
    return (count > 0) ? sum / count : 0.0;
}
int main() {
    int m, n;
    std::cin >> m >> n;
    std::vector<Purchase> purchases(m);
    for (int i = 0; i < m; i++) {
        std::cin >> purchases[i].date >> purchases[i].product >> purchases[i].price;
    }
    double keyboardAvgPrice = calculateAveragePrice(purchases, "keyboard", n);
    double mouseAvgPrice = calculateAveragePrice(purchases, "mouse", n);
    std::cout << std::fixed;
    std::cout.precision(1);
    std::cout << keyboardAvgPrice << std::endl;
    std::cout << mouseAvgPrice << std::endl;
	return 0;
}

请注意，这里使用了C++11标准的日期时间库，并假设输入的日期格式为”YYYY-MM-DD”。还使用strptime()函数将日期字符串解析为std::tm结构体，然后将其转换为std::chrono::system_clock时间点进行比较。最后，通过与当前日期进行比较来判断日期是否在当前日期之前。

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