本题题解，只需根据题意算出年龄，再代入公式即可。需要特别注意闰年。

本题完整代码：

#include <iostream>
#include <cmath>
#include <iomanip>
#include <ctime>

// 判断闰年
bool isLeap(int year) {
    return (year % 4 == 0 && year % 100 != 0) || (year % 400 == 0);
}

// 获取某年某月的天数
int daysInMonth(int year, int month) {
    static const int days[] = {31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};
    if (month == 2 && isLeap(year)) {
        return 29;
    }
    return days[month - 1];
}

// 计算精确年龄（以年为单位）
double calculateAge(int birthYear, int birthMonth, int birthDay,
                    int currentYear, int currentMonth, int currentDay) {
    // 先按年份粗略计算
    int ageYears = currentYear - birthYear;

    // 如果还没过生日，减一岁
    if (currentMonth < birthMonth ||
        (currentMonth == birthMonth && currentDay < birthDay)) {
        ageYears--;
    }

    // 如果年龄已经是负数，说明出生日期在未来
    if (ageYears < 0) return -1.0;

    // 计算生日到今天的天数（今年已过的天数）
    int daysSinceBirthday = 0;
    if (currentMonth > birthMonth ||
        (currentMonth == birthMonth && currentDay >= birthDay)) {
        // 生日已过，从生日到今天
        int y = currentYear;
        for (int m = birthMonth; m < currentMonth; ++m) {
            daysSinceBirthday += daysInMonth(y, m);
        }
        daysSinceBirthday += (currentDay - birthDay);
    } else {
        // 生日未过，从生日到年底，再加今年已过天数（这种情况不会进入，因已减1岁）
        // 实际上我们只在生日已过时才加小数部分
        daysSinceBirthday = 0;
    }

    // 计算今年生日到明年生日的总天数（用于小数部分）
    int daysInYearAfterBirthday = 0;
    int y = currentYear;
    for (int m = birthMonth; m <= 12; ++m) {
        daysInYearAfterBirthday += daysInMonth(y, m);
    }
    for (int m = 1; m < birthMonth; ++m) {
        daysInYearAfterBirthday += daysInMonth(y + 1, m);
    }

    double fractional = static_cast<double>(daysSinceBirthday) / daysInYearAfterBirthday;
    return static_cast<double>(ageYears) + fractional;
}

int main() {
    int birthYear, birthMonth, birthDay;
    std::cin >> birthYear >> birthMonth >> birthDay;

    // 获取当前本地时间
    std::time_t now = std::time(nullptr);
    std::tm* localTime = std::localtime(&now);
    int currentYear = localTime->tm_year + 1900;
    int currentMonth = localTime->tm_mon + 1; // tm_mon: 0-11
    int currentDay = localTime->tm_mday;

    // 验证输入合理性（简单检查）
    if (birthMonth < 1 || birthMonth > 12 ||
        birthDay < 1 || birthDay > daysInMonth(birthYear, birthMonth)) {
        // 输入无效，保守输出 0.00%
        std::cout << "0.00%" << std::endl;
        return 0;
    }

    // 计算精确年龄
    double age = calculateAge(birthYear, birthMonth, birthDay,
                              currentYear, currentMonth, currentDay);

    if (age < 0) {
        std::cout << "0.00%" << std::endl;
        return 0;
    }

    const double START_AGE = 3.0;
    const double MAX_LIFESPAN = 100.0;

    double percentage;
    if (age <= START_AGE) {
        percentage = 0.0;
    } else if (age >= MAX_LIFESPAN) {
        percentage = 100.0;
    } else {
        double y = std::log(age / START_AGE) / std::log(MAX_LIFESPAN / START_AGE);
        percentage = y * 100.0;
        // 限制范围
        if (percentage < 0) percentage = 0.0;
        if (percentage > 100) percentage = 100.0;
    }

    std::cout << std::fixed << std::setprecision(2) << percentage << "%" << std::endl;

    return 0;
}