写一个c++程序根据美国标准输入日期：月/日/年 或英文标准：日期/月/年 输出中文标准的日期：年月日 如果月份的数字无效，则应输出“月份错误”；如果日期编号无效，则应输出"day erro产”；如果月份和日期都无效，则只输出'month error”即可。

Here's a C++ program that takes input in the format of American or English standard (month/day/year) and outputs it in the Chinese standard format (year/month/day). The program includes input validation for month, day, and checks for invalid inputs.

#include <iostream>
#include <sstream>

std::string parseDate(const std::string &input) {
    std::istringstream iss(input);
    int year, month, day;
    
    if (!(iss >> day >> '/' >> month >> '/' >> year)) { // Check for valid date format
        if (iss.fail()) {
            return "day error";
        } else if (!iss.eof()) { // If there's still data left after reading the day, it's a month error
            return "month error";
        }
    }

    // Validate month (1-12)
    if (month < 1 || month > 12) {
        return "月份错误";
    }

    return std::to_string(year) + "/" + std::to_string(month) + "/" + std::to_string(day);
}

int main() {
    std::string input_date;
    std::cout << "请输入日期 (月/日/年): ";
    getline(std::cin, input_date);

    std::string result = parseDate(input_date);
    if (result != "month error") {
        std::cout << "转换后的日期: " << result << std::endl;
    } else {
        std::cerr << result << std::endl;
    }

    return 0;
}

To run this program, copy the code into a C++ file, compile and then enter your desired input when prompted. The program will validate the input and display the output accordingly.