Question

C Programming Please write a single function and not the whole program

Can you please provide comments and explanations for all questions. Thank you

Write a single function for the following:

void split_date(int day_of_year, int year, int *month, int *day);

            day_of_year is an integer between 1 and 366, specifying a particular day within the year

designated by the parameter year. Month and day point to variables in which the function
will store the equivalent month (1 – 12) and day within the month (1 – 31)

The question is trying to ask you to write a single function in C that takes a day of the year (1-366) and calculates which month and which day of the month corresponds to that day of in the month. So a day of the year of let's 15 would return 1 (for the month - January) and 15 for the day of the month. The second parameter (year) is needed because leap years have 366 days and non-leap years have 365 days.

Answer 1

int check_Leap(int year)
{
if( (year%4 == 0 && year%100 != 0) || (year%400 == 0) )
return 1;       //is a leap year
else
return 0;       //is not a leap year
}

void split_date(int day_of_year, int year, int *month, int *day)
{
   //At first check whether the given year is a leap year or not
   //We are storing 0 in is_Leap_Year variable if it is not a leap year
   //else 1 for a leap year using function check_Leap()
   int is_Leap_Year = check_Leap(year);
  
   if (day_of_year <1 || day_of_year>366)
       printf("Invalid Day of Year\n");  
       //if user enters day_of_year out of the range
  
   else if(year<1000 || year>9999)
       printf("Invalid year\n");
       //if user enters year out of the range
  
   else
   {
       //initializing total number of days in every month in an array
       int month_days[] = {31,28,31,30,31,30,31,31,30,31,30,31};
      
       //changing total number of days in February as 29
       //if year is a leap year
       month_days[1] += is_Leap_Year;      
       //e.g. for 2016 as leap year, month_days[1] = 28 + 1
      
       int i, d = day_of_year;
      
       for(i=0; d > month_days[i]; i++)
           d -= month_days[i];
       //here in this for loop, total number of days of every month is
       //being subtracted from day_of_year until day_of_year becomes
       //less than total number of days in a particular month.
       //after loop ends, i stores the actual value of month
       //so we store the month's answer
      
       *month = ++i;
       //since the array month_days[] has 0 index counting,
       //so February has indexing 1. We incremented i to store 2 for
       //February in month.
      
       *day = d;
       //the remaining value of d holds the actual answer for date
       //when d becomes less than total number of days in a month
       //then d is the date we are looking for.
      
   }
}

INPUT: day_of_year: 234       year: 2008
OUTPUT: *day = 21 *month = 8

Explanation:
Since 2008 is a leap year, month_days[] becomes
month_days[] = {31,29,31,30,31,30,31,31,30,31,30,31}

Now checking for loop:
d = 234;
for(i=0; d > month_days[i]; i++)
   d -= month_days[i];

#Pass 0:
234 > month_days[0] ----> 234>31 ---> YES
Subtract: d = 234-31 = 203
i++;

#Pass 1:
203 > month_days[1] ----> 203>29 ---> YES
Subtract: d = 203-29 = 174
i++;

#Pass 2:
174 > month_days[2] ----> 174>31 ---> YES
Subtract: d = 174-31 = 143
i++;

#Pass 3:
143 > month_days[3] ----> 143>30 ---> YES
Subtract: d = 143-30 = 113
i++;

#Pass 4:
113 > month_days[4] ----> 113>31 ---> YES
Subtract: d = 113-31 = 82
i++;

#Pass 5:
82 > month_days[5] ----> 82>30 ---> YES
Subtract: d = 82-30 = 52

#Pass 6:
52 > month_days[6] ----> 52>31 ---> YES
Subtract: d = 52-31 = 21
i++;

#Pass 7:
21 > month_days[7] ----> 21>31 ---> NO
EXIT from the Loop

So day becomes 21 and month becomes ++i = 8.