用c++写一个程序输入一个日期后面输入增加的天数，最后输出增加后的日期

#include <stdio.h>

int main()
{
    int year, month, day;
    int add_days, days_in_month;
    
    printf("请输入年份：");
    scanf("%d", &year);
    printf("请输入月份：");
    scanf("%d", &month);
    printf("请输入日期：");
    scanf("%d", &day);
    printf("请输入增加的天数：");
    scanf("%d", &add_days);
    
    // 计算当前日期是当年的第几天
    int days = 0;
    for (int i = 1; i < month; i++) {
        switch (i) {
            case 1: case 3: case 5: case 7: case 8: case 10: case 12:
                days += 31; break;
            case 4: case 6: case 9: case 11:
                days += 30; break;
            case 2:
                if ((year % 4 == 0 && year % 100 != 0) || year % 400 == 0)
                    days += 29; // 闰年2月29天
                else
                    days += 28; // 平年2月28天
                break;
        }
    }
    days += day;
    
    // 增加天数
    days += add_days;
    
    // 计算增加后的日期
    day = days % 100; days /= 100;
    month = days % 100; days /= 100;
    year += days;
    
    // 处理月份和天数
    if (month > 12) {
        year += month / 12;
        month %= 12;
    }
    days_in_month = 31; // 假定是31天
    switch (month) {
        case 4: case 6: case 9: case 11:
            days_in_month = 30; break;
        case 2:
            if ((year % 4 == 0 && year % 100 != 0) || year % 400 == 0)
                days_in_month = 29;
            else
                days_in_month = 28;
            break;
    }
    if (day > days_in_month) {
        month++;
        day -= days_in_month;
        if (month > 12) {
            year += month / 12;
            month %= 12;
        }
    }
    
    // 输出增加后的日期
    printf("增加后的日期为：%04d年%02d月%02d日\n", year, month, day);
    
    return 0;
}