LTD Puzzle 10 - Weekends between two dates

[AlexCuse]

This week's puzzle is a simple one. Write a program that will take two dates as inputs, and output the number of weekends between them.

To be consistent, the ranges will include the start and end dates. And we will count 1/2 weekends.

Have fun!

[shamsm]

A solution in java using the existing Calendar class. I have counter Saturday and Sunday as weekends.

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1. import java.util.Calendar;
2.  
3. /**
4.  * @author Shams
5.  * @version Aug 11, 2008 4:15:22 PM
6.  */
7. public class Puzzle10 {
8.  
9.     public static void main(String[] args) {
10.  
11.         final int[] eStartDateInput = {1 /* day */, 1 /* month */, 2000 /* year */};
12.         final int[] eEndDateInput = {31 /* day */, 12 /* month */, 2008 /* year */};
13.  
14.         final Calendar eStartDate = Calendar.getInstance();
15.         eStartDate.set(Calendar.DATE, eStartDateInput[0]);
16.         eStartDate.set(Calendar.MONTH, eStartDateInput[1] - 1);
17.         eStartDate.set(Calendar.YEAR, eStartDateInput[2]);
18.         System.out.println("Start Date: " + eStartDate.getTime());
19.  
20.         final Calendar eEndDate = Calendar.getInstance();
21.         eEndDate.set(Calendar.DATE, eEndDateInput[0]);
22.         eEndDate.set(Calendar.MONTH, eEndDateInput[1] - 1);
23.         eEndDate.set(Calendar.YEAR, eEndDateInput[2]);
24.         System.out.println("End Date: " + eEndDate.getTime());
25.  
26.         final long eTimeDiffInMillis = eEndDate.getTimeInMillis() - eStartDate.getTimeInMillis();
27.         final long eTimeDiffInDays = (eTimeDiffInMillis / (24 * 60 * 60 * 1000)) + 1;
28.         final long eCompleteWeeksInBetween = eTimeDiffInDays / 7;
29.         final int eStartDayOfWeek = eStartDate.get(Calendar.DAY_OF_WEEK);
30.         final int eEndDayOfWeek = eEndDate.get(Calendar.DAY_OF_WEEK);
31.  
32.         long eResult = eCompleteWeeksInBetween * 2;
33.         for (int i = eStartDayOfWeek, j = 0; j <= Math.abs(eEndDayOfWeek - eStartDayOfWeek); i++, j++) {
34.             switch ((i % 7) + 1) {
35.                 case Calendar.SATURDAY:
36.                 case Calendar.SUNDAY:
37.                     eResult++;
38.                     break;
39.             }
40.         }
41.  
42.         System.out.println("Number of weekends: " + eResult);
43.     }
44. }
45.  

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And the output is below.

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1. Start Date: Sat Jan 01 16:37:58 CST 2000
2. End Date: Wed Dec 31 16:37:58 CST 2008
3. Number of weekends: 939
4.  

[AlexCuse]

F# has some really cool functions for things like this

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1. #light
2. open System
3.  
4. let getdate n =
5.     printfn "please enter a value for date #%d:\n" n
6.     let x = DateTime.Parse(Console.ReadLine())  
7.     x
8.    
9. let weekends (d1:System.DateTime) (d2:System.DateTime) =
10.     let potentialDays = [0 .. (d2-d1).Days]
11.  
12.     let wknd = potentialDays |> Seq.fold
13.                 (fun ctr x-> if d1.AddDays((float)x).DayOfWeek = DayOfWeek.Saturday
14.                                 or d1.AddDays((float)x).DayOfWeek = DayOfWeek.Sunday then
15.                                 ctr + 0.5
16.                              else
17.                                 ctr) 0.00
18.     wknd
19.                        
20. let sd = getdate 1
21. let ed = getdate 2
22. printf "Number of weekends is "
23. print_any (weekends sd ed)
24.  
25. Console.ReadLine()

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[SQLDenis]

T-SQL version

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1. DECLARE @s AS DATETIME, @e AS DATETIME;
2. SET @s = '20000101';
3. SET @e = '20081231';
4. DECLARE @range INT;
5.  
6. SET @range = DATEDIFF(DAY, @s, @e);
7.  
8.         SELECT  
9.             @range / 7 * 2 + @range % 7 -  
10.             (
11.                 SELECT COUNT(*)  
12.             FROM
13.                 (
14.                     SELECT 1 AS d
15.                     UNION ALL SELECT 2  
16.                     UNION ALL SELECT 3  
17.                     UNION ALL SELECT 4  
18.                     UNION ALL SELECT 5  
19.                     UNION ALL SELECT 6  
20.                     UNION ALL SELECT 7
21.                 ) weekdays
22.                 WHERE d <= @range % 7  
23.                 AND DATENAME(WEEKDAY, @e - d + 1)  
24.                 IN
25.                 (
26.                     'Monday','Tuesday' ,'Wednesday','Thursday','Friday'
27.                 )
28.             )
29.    
30.  
31.  

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[tisodotsk]

My solution in PHP:

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1. <?php
2. //ltd10.php - LTD Puzzle 10: Weekends between two dates
3. //via Topic2510: LTD Puzzle 10 - Weekends between two dates
4. //------------------------------------------------------------------------------
5. function WeekendsCount($startdate, $enddate)
6. {
7.     $days=1+(strtotime($enddate)-strtotime($startdate))/86400;
8.     $count=floor($days/7);//full weeks means full weekends
9.     $mod=$days % 7;
10.     $dayofweek=date('N', strtotime($startdate));//N: returns from 1 for Monday to 7 for Sunday
11.     if($mod != 0){//check for other weekend days:
12.         if($dayofweek == 7){$count+=0.5;}
13.         elseif(7 <= ($mod+$dayofweek)){$count+=0.5*ceil(($mod+$dayofweek)/7);}
14.     }
15.     return $count;
16. }
17. //------------------------------------------------------------------------------
18. //test:
19. for($i=11; $i <= 17; $i++){//start from every day of the week
20.     for($j=$i; $j < $i+14; $j++){//lenght up to 14 days
21.         Result('200808'.$i, '200808'.$j);
22.     }
23. }
24. //------------------------------------------------------------------------------
25. //test function:
26. function Result($startdate, $enddate)
27. {
28.     echo 'From '.$startdate.' to '.$enddate.' are '.WeekendsCount($startdate, $enddate).' weekends. |';
29.     //create calendar:
30.     $start=strtotime($startdate);
31.     $end=strtotime($enddate);
32.     for($i=$start; $i <= $end; $i+=86400){
33.         if(date('N', $i) <= 5){echo date('d', $i).'|';}//normal days
34.         else{echo '<b>'.date('d', $i).'</b>|';}//weekend days are bold
35.     }
36.     echo '<br>';
37. }
38. //------------------------------------------------------------------------------
39. ?>

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Output (first 14 lines):

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1. From 20080811 to 20080811 are 0 weekends. |11|
2. From 20080811 to 20080812 are 0 weekends. |11|12|
3. From 20080811 to 20080813 are 0 weekends. |11|12|13|
4. From 20080811 to 20080814 are 0 weekends. |11|12|13|14|
5. From 20080811 to 20080815 are 0 weekends. |11|12|13|14|15|
6. From 20080811 to 20080816 are 0.5 weekends. |11|12|13|14|15|16|
7. From 20080811 to 20080817 are 1 weekends. |11|12|13|14|15|16|17|
8. From 20080811 to 20080818 are 1 weekends. |11|12|13|14|15|16|17|18|
9. From 20080811 to 20080819 are 1 weekends. |11|12|13|14|15|16|17|18|19|
10. From 20080811 to 20080820 are 1 weekends. |11|12|13|14|15|16|17|18|19|20|
11. From 20080811 to 20080821 are 1 weekends. |11|12|13|14|15|16|17|18|19|20|21|
12. From 20080811 to 20080822 are 1 weekends. |11|12|13|14|15|16|17|18|19|20|21|22|
13. From 20080811 to 20080823 are 1.5 weekends. |11|12|13|14|15|16|17|18|19|20|21|22|23|
14. From 20080811 to 20080824 are 2 weekends. |11|12|13|14|15|16|17|18|19|20|21|22|23|24|

edit: change some comments, you know - english...

[Remou]

VBA. I hope.

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1. Function RetWE(dteStart, dteEnd)
2.     we = DateDiff("ww", dteStart, dteEnd)
3.    
4.     If Weekday(dteEnd) = 7 Then we = we + 1
5.     If Weekday(dteStart) = 1 Then we = we + 1
6.    
7.     RetWE = we
8. End Function

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[AlexCuse]

Remou, its too simple. What's the fun in that

[traingamer]

Remou's doesn't take into account the partial weekends.

e.g. Sunday to Saturday - two week span - the answer should be 2 (.5 for Sunday, 1 for the middle weekend and .5 for the concluding Saturday) - code returns 3

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1. ?Retwe(#3-2-2008#, #3-15-2008#)
2.  3

Sunday to Saturday single week similarly returns 2 when the answer should be 1.

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1. ?Retwe(#3-2-2008#, #3-8-2008#)
2.  2

I had virtually identical code started using mod 7 and number of days, but didn't get around to finishing it because I ran into the same problems (and didn't take the time to correct).

[Remou]

I interpreted

To be consistent, the ranges will include the start and end dates. And we will count 1/2 weekends.

To mean that partial weekends counted as 1, therefore .5,1,.5 would equal three, not 2. Similarly, Sunday to Saturday is .5,.5 and by those rules equals 2. That is, the range encompasses two weekends.

Have I misinterpreted the rules?

[traingamer]

Have I misinterpreted the rules?

Maybe I did.

[AlexCuse]

I guess that is less than clear. I meant we would count 1/2 weekend as 1/2, but did leave some room for interpretation.

I collapsed under the pressure of delivering the great one's message.

[Emtucifor]

I gave it up after a short while because I just don't have the time. But if I had interpreted it that 1/2 weekends would be 0.5 instead of 1 each, I think I would have finished!

[SQLDenis]

I interpreted it as 1/2 + 1 + 1/2 = 2

[AlexCuse]

that's what I intended Denis. Sorry for any confusion.

[Emtucifor]

And 1 + 1/2 = 1.5?

[SQLDenis]

mmmm, now my code is incorrect

SET @s = '20080816';
SET @e = '20080823';

should give 1.5

Now I don't remember what I understood when I did this, I made it match whatever the person before me had

[traingamer]

Late entry

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1. Public Function Wkends(sdte As Date, edte As Date)
2. Dim dowend As Integer
3. Dim remain As Integer
4. Dim numwkends As Single
5.     If edte < sdte Then
6.         Debug.Print "Start date can not be greater than end date!"
7.     Else
8.         dowend = Weekday(edte)  '  last day in range sun = 1...sat = 7
9.         remain = (DateDiff("d", sdte, edte + 1) Mod 7)  ' remainder days after removing whole weeks
10.         numwkends = DateDiff("d", sdte, edte + 1) \ 7   ' number of whole weeks
11.         If remain > 0 Then
12.             ' if there are extra days & end date is saturday add .5
13.             ' if remainder = day of week add .5 for Sunday
14.             ' if remainder > day of week add 1 for full weekend
15.             numwkends = numwkends + ((dowend = 7) * -0.5) _
16.              + ((dowend = remain) * -0.5) _
17.              + ((dowend < remain) * -1)
18.         End If
19.         Debug.Print "There are " & numwkends & " weekends between " & sdte & " and " & edte
20.     End If
21. End Function 
22.  
23. ' There are 1.5 weekends between 07/04/2008 and 07/12/2008
24. ' There are 5 weekends between 07/01/2008 and 08/05/2008
25. ' There are 1 weekends between 08/01/2008 and 08/04/2008
26. ' There are 1 weekends between 08/01/2008 and 08/08/2008
27. ' There are 0.5 weekends between 08/03/2008 and 08/03/2008
28.  

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[chrissie1]

The winners have been determined!

Peoples Champ: shamsm

LTD Admins Champion - traingamer.

Congratulations!