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# Thursday Code Puzzler: How Many Weekends?

09.12.2012
| 5063 views |

Thursday is code puzzler day here at DZone. The idea is simple: solve the coding problem as efficiently as you can, in any language or framework that you find suitable.

Note: Even though there really is nothing stopping you from finding a solution to this on the internet, try to keep honest, and come up with your own answer.  It's all about the participation!

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How Many Weekends?

Write a function that takes two dates and returns the number of weekends between those dates. If either of the start or end dates is a weekend, you can count that. And whether it's a Saturday or Sunday (doesn't need to include both), it counts.

Catch up on all our previous puzzlers here.

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### Neeraj Khapre replied on Thu, 2012/09/13 - 4:49am

```public class WeekendCalculater {

public static void main(String[] args) throws ParseException {
SimpleDateFormat sdf = new SimpleDateFormat("MM/dd/yyyy");

Calendar startDate = Calendar.getInstance();
startDate.setTime(sdf.parse("09/06/2012"));

Calendar endDate = Calendar.getInstance();
endDate.setTime(sdf.parse("09/09/2012"));

System.out.println("Total no. of Weekends are : "
+ calculateWeekends(startDate, endDate));
}

public static int calculateWeekends(Calendar startDate, Calendar endDate) {
// Return 0 if startDate and endDate are same
if (startDate.equals(endDate)) {
return 0;
}

int weekend_count = 0;
int count = 0;

while (startDate.compareTo(endDate) == -1) {

if (startDate.get(Calendar.DAY_OF_WEEK) == Calendar.SUNDAY
|| startDate.get(Calendar.DAY_OF_WEEK) == Calendar.SATURDAY) {
count++;
if (count == 2) {
weekend_count++;
count = 0;
}
}
}
return weekend_count;
}
}
```

### Leandro Santos replied on Thu, 2012/09/13 - 10:32am

Here is the code in ruby:

`class WeekendsCalculator  attr_reader :days  def initialize(start_at,end_at)    @days = parse_range(start_at,end_at)  end  def parse_range(start_at, end_at)    if start_at.is_a?(String) && end_at.is_a?(String)      Date.parse(start_at)..Date.parse(end_at)    elsif start_at.is_a?(Date) && end_at.is_a?(Date)      start_at..end_at    else      raise "Start_at and end_at should be either strings or date objects"    end  end  def weekends    days.inject(0) do |weekends,day|      weekends += 1 if day.saturday?      weekends    end  endendc = WeekendsCalculator.new('2012-08-01', '2012-09-07')puts "The number of weekends is #{c.weekends}"`

### Vijay Nathani replied on Thu, 2012/09/13 - 9:49pm

Groovy solution using open source library jodaTime.

```import org.joda.time.*;
class ComputeWeekends {
private def st, en;
private int pre;
private boolean isWeekend(date) { [DateTimeConstants.SATURDAY, DateTimeConstants.SUNDAY].contains(date.dayOfWeek().get())}
private def gotoMiddleOfWeek(startOrEnd) {
boolean lastDateWeekend = false
while (st <= en ) {
def d = startOrEnd?st:en
if (d.dayOfWeek().get() == DateTimeConstants.WEDNESDAY) return
pre += (isWeekend(d) && !lastDateWeekend)?1:0
lastDateWeekend = isWeekend(d)
startOrEnd?(st=st.plusDays(1)):(en=en.minusDays(1))
}
}
def weekendsBetween(start,end) {
if (start > end) return 0
(st, en, pre) = [ start, end, 0]
gotoMiddleOfWeek(true)
gotoMiddleOfWeek(false)
Days.daysBetween(st,en).days / DateTimeConstants.DAYS_PER_WEEK + pre
}
}
println new ComputeWeekends().weekendsBetween(new DateMidnight(2012, 9, 4), new DateMidnight(2012, 9, 22)) //prints 3```

### ebenezer raj replied on Thu, 2012/09/13 - 2:04pm

In q { x:x[0]+til 1+x[1]-x[0]; x:x-`week\$x; x[where x within (5 6)]:-1; x:?[(prev x)=-1;0;x]; count x[where x=-1] }[(2012.09.01;2012.09.13)] prints out 2

### Joe Colburn replied on Thu, 2012/09/13 - 6:43pm

```function weekends(\$date1, \$date2) {
\$epoch1 = strtotime(\$date1);
\$epoch2 = strtotime(\$date2);
\$weekends = floor(((\$epoch2 - \$epoch1) / 86400) / 7);
if (substr(date("D", \$epoch1), 0, 1) == "S") {
\$weekends++;
}
if (substr(date("D", \$epoch2), 0, 1) == "S") {
\$weekends++;
}

return \$weekends;
}
```

### Vijay Nathani replied on Thu, 2012/09/13 - 9:51pm in response to: Joe Colburn

Will this code work for boundary conditions e.g. weekends between 8 and 9-Sep-2012?

### Joe Colburn replied on Thu, 2012/09/13 - 11:47pm in response to: Vijay Nathani

Good question... If you mean when the first date is Sep 8 2012 and the second is Sep 9 2012, I believe it will fail, counting it as 2 weekends, but that should be the only failing scenario.  Good catch!

### Vijay Nathani replied on Fri, 2012/09/14 - 12:10am in response to: Joe Colburn

Even when both start and end dates are the same weekend date e.g. 8-Sep-2012 , the code will fail.

If start date is after end date, then too the code fails.

If start date is 9-Sep-12 and end date is 16-Sep-12, then too the code fails.