CareerCup

Assume these two functions :
1. addMonths(date, n): Adds exactly 'n' months to 'date'
2. compare(date1, date2): Returns -1, 0, 1 depending on the date values
These functions are very easy to code. Then the solution for the problem will be the following function:

// this function returns
// -1 if the two dates are less than one month apart
// 0 if the two dates are exactly one month apart
// 1 if the two dates are more than one month apart
int compareDateMonths(Date date1, Date date2)
{
Date earlier;
Date later;
int comparison = compare (date1, date2);
if ( comparison == 0)
{
return -1;
}
else if (comparison == -1)
{
earlier = date1;
later = date2;
}
else
{
earlier = date2;
later = date1;
}

addMonths(earlier, 1);

return -(compare(earlier, later));
}

I think the point should be to minimize the number of arithematic and comparison operations, not just get the right answer. So a number of pruning steps are required to return false.

1. if difference between years >= 2 then false
2. if difference between month names >= 2, like "Jan" and "Apr" (1 and 4) then false

now you serialize the date, by 1 being the first date of the smaller month, +30 (or whatever) being the first date of the second month (include difference in year too).. then convert both dates into this format, subtract, and see if its less than 30 days..

Also cases like February, with 28 days, might need to be special cases.

find the date which is less than other
add 30 days to it say date3

now compare it to the other

if they are equal (exactly 30 days apart)
if date3 is greater (less than 30 days apart)
if date3 is lesser( more than 30 days apart)

Matchless makes sense!
How about situation: 02/01/07 - 03/01/07?
They are month apart but above algorithm would return false!

Date1:
D1YY
D1MM
D1DD

Date2:
D2YY
D2MM
D2DD

If |D2YY - D1YY| > 1 => More than month apart
If |D2YY - D1YY| = 0 => Same Year
If |D2MM - D1MM | > 1 => More than a month apart
If |D2MM - D1MM| = 0 => Same month => Less than month apart
If |D2MM - D1MM| = 1
If |D2DD - D1DD| = 0 => Month Apart
If D2MM > D1MM
If D2DD > D1DD => More than a month
else => Less than a month
else
If D1DD > D2DD => More than a month
else => Less than a month

and so on... it is so tiring to write all this :)

example:
dd/mm/yyyy
-Assuming no leap years
-All months have 30 days

date1 = 04/06/2007
date2 = 09/07/2007

compute date1 and date2 as follows:
date1 = 2006*365 + 6*30 + 4
date2 = 2006*365 + 7*30 + 9

check modulus of |date2 - date1| > 30

If we are allowed to use a method that given a date converts it into number of seconds from Jan 1 1970.

And then consider a month as 4 weeks = 28 days and just check if the difference between the dates in 28 days?

If we need to be strict abt 30,31,28 write up some if statements...