#include<stdio.h>int daytab[2][13] = {                    {0, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31},  // 平年的月份                    {0, 31, 29, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31},  // 闰年的月份                    };/* 把某月某日这种日期表示形式转换为某年中第几天 */int day_of_year(int year, int month, int day){    int result = 0;    int flag = year%4 == 0 && year%100 != 0 || year%400==0; //判断是否为闰年。是则返回1，否则返回0    int i = 0;    // 错误检查    if (year < 1752 || month < 1 || month > 12 || day < 1)        return -1;    if(day > daytab[flag][month]){        return -1;    }    // 循环    for(; i < month; i++){        result += daytab[flag][i];    }    result += day;    return result;}/* 把某年中第几天表示形式转换为某月某日这种日期形式 */int month_day(int year, int theDays, int *pmonth, int *pday){    int flag = year%4 == 0 && year%100 != 0 || year%400==0; //判断是否为闰年。是则返回1，否则返回0    int i = 0;    // 错误检查    if (year < 1752 || theDays < 1){        return -1;    }    if ((flag && theDays > 366) || (!flag && theDays > 365)){        return -1;    }    for(; theDays > daytab[flag][i] && i <= 12 ; i++){        theDays -= daytab[flag][i];    }    *pmonth = i;    *pday = theDays;    return 0;}/* 主函数 */void main(){    int month, day;    printf("%d\n",day_of_year(1988, 3, 1));    month_day(1988, 61, &month, &day);    printf("month = %d, day = %d\n", month, day);}