Last Friday of each month
Write a program or a script that returns the last Fridays of each months of a given year provided as argument on the command line.
Example of an expected output:
./last_fridays 2012 2012-01-27 2012-02-24 2012-03-30 2012-04-27 2012-05-25 2012-06-29 2012-07-27 2012-08-31 2012-09-28 2012-10-26 2012-11-30 2012-12-28
- Cf.
C
<lang c>#define _XOPEN_SOURCE
- include <stdio.h>
- include <time.h>
int main(int c, char *v[]) { int days[] = {31,29,31,30,31,30,31,31,30,31,30,31}; int m, y, w; struct tm tm; char buf[32];
if (c < 2 || !sscanf(v[1], "%d", &y)) return 1;
days[1] -= y % 4 || (y % 100 && ! (y % 400)); sprintf(buf, "%d-1-1", y); strptime(buf, "%Y-%m-%d", &tm); w = tm.tm_wday - 1; /* day of week for zeroth of Jan */
for(m = 0; m < 12; m++) { w = (w + days[m]) % 7; printf("%d-%02d-%d\n", y, m + 1, days[m] + (w < 5 ? -2 : 5) - w); }
return 0; }</lang>
C++
called with ./last_fridays 2012
<lang cpp>#include <boost/date_time/gregorian/gregorian.hpp>
- include <iostream>
- include <cstdlib>
int main( int argc , char* argv[ ] ) {
using namespace boost::gregorian ;
greg_month months[ ] = { Jan , Feb , Mar , Apr , May , Jun , Jul , Aug , Sep , Oct , Nov , Dec } ; greg_year gy = atoi( argv[ 1 ] ) ; for ( int i = 0 ; i < 12 ; i++ ) { last_day_of_the_week_in_month lwdm ( Friday , months[ i ] ) ; date d = lwdm.get_date( gy ) ; std::cout << d << std::endl ; } return 0 ;
}</lang> Output:
2012-Jan-27 2012-Feb-24 2012-Mar-30 2012-Apr-27 2012-May-25 2012-Jun-29 2012-Jul-27 2012-Aug-31 2012-Sep-28 2012-Oct-26 2012-Nov-30 2012-Dec-28
Icon and Unicon
This will write the last fridays for every year given as an argument. There is no error checking on the year.
<lang Icon>procedure main(A) every write(lastfridays(!A)) end
procedure lastfridays(year) every m := 1 to 12 do {
d := case m of { 2 : if IsLeapYear(year) then 29 else 28 4|6|9|11 : 30 default : 31 } # last day of month z := 0 j := julian(m,d,year) + 1 # first day of next month until (j-:=1)%7 = 4 do z -:=1 # backup to last friday=4 suspend sprintf("%d-%d-%d",year,m,d+z) }
end
link datetime, printf</lang>
printf.icn provides formatting datetime.icn provides julian and IsLeapYear
Output:
last_fridays.exe 2012 2012-1-27 2012-2-24 2012-3-30 2012-4-27 2012-5-25 2012-6-29 2012-7-27 2012-8-31 2012-9-28 2012-10-26 2012-11-30 2012-12-28
J
<lang j>require'dates' last_fridays=: 12 {. [:({:/.~ }:"1)@(#~ 5 = weekday)@todate (i.366) + todayno@,&1 1</lang>
In other words, start from January 1 of the given year, and count forward for 366 days, keeping the fridays. Then pick the last friday within each represented month. Then pick the first 12 (since on a non-leap year which ends on a thursday we would get an extra friday).
Example use:
<lang j> last_fridays 2012 2012 1 27 2012 2 24 2012 3 30 2012 4 27 2012 5 25 2012 6 29 2012 7 27 2012 8 31 2012 9 28 2012 10 26 2012 11 30 2012 12 28</lang>
Java
<lang java5>import java.util.Calendar; import java.util.GregorianCalendar;
public class LastFriday {
private static int[] months = {Calendar.JANUARY, Calendar.FEBRUARY,
Calendar.MARCH, Calendar.APRIL, Calendar.MAY, Calendar.JUNE,
Calendar.JULY, Calendar.AUGUST, Calendar.SEPTEMBER, Calendar.OCTOBER,
Calendar.NOVEMBER, Calendar.DECEMBER};
public static void main(String[] args){
int year = Integer.parseInt(args[0]);
boolean leapYear = new GregorianCalendar().isLeapYear(year);
for(int month:months){
int days = 31;
switch(month){
case Calendar.SEPTEMBER:
case Calendar.APRIL:
case Calendar.JUNE:
case Calendar.NOVEMBER:
days = 30;
break;
case Calendar.FEBRUARY:
days = leapYear ? 29 : 28;
default:
}
GregorianCalendar date = new GregorianCalendar(year, month, days);
while(date.get(Calendar.DAY_OF_WEEK) != Calendar.FRIDAY){
date.add(Calendar.DAY_OF_MONTH, -1);
}
System.out.println((date.get(Calendar.MONTH) + 1) + "-"
+ date.get(Calendar.DAY_OF_MONTH));
}
}
}</lang>
Output (for java LastFriday 2012
):
1-27 2-24 3-30 4-27 5-25 6-29 7-27 8-31 9-28 10-26 11-30 12-28
OCaml
<lang ocaml>#load "unix.cma" open Unix
let usage() =
Printf.eprintf "%s <year>\n" Sys.argv.(0); exit 1
let print_date t =
Printf.printf "%d-%02d-%02d\n" (t.tm_year + 1900) (t.tm_mon + 1) t.tm_mday
let is_date_ok tm t =
(tm.tm_year = t.tm_year && tm.tm_mon = t.tm_mon && tm.tm_mday = t.tm_mday)
let () =
let _year = try int_of_string Sys.argv.(1) with _ -> usage() in let year = _year - 1900 in let fridays = Array.make 12 (Unix.gmtime 0.0) in for month = 0 to 11 do for day_of_month = 1 to 31 do let tm = { (Unix.gmtime 0.0) with tm_year = year; tm_mon = month; tm_mday = day_of_month; } in let _, t = Unix.mktime tm in if is_date_ok tm t (* check for months that have less than 31 days *) && t.tm_wday = 5 (* is a friday *) then fridays.(month) <- t done; done; Array.iter print_date fridays</lang>
Output:
$ ocaml last_fridays.ml 2012 2012-01-27 2012-02-24 2012-03-30 2012-04-27 2012-05-25 2012-06-29 2012-07-27 2012-08-31 2012-09-28 2012-10-26 2012-11-30 2012-12-28
Pike
<lang Pike>int(0..1) last_friday(object day) {
return day->week_day() == 5 && day->month_day() > day->month()->number_of_days()-7;
}
int main(int argc, array argv) {
array days = filter(Calendar.Year((int)argv[1])->months()->days()[*], last_friday); write("%{%s\n%}", days->format_ymd()); return 0;
}</lang>
Ruby
<lang ruby>require 'date'
def last_friday(year, month)
if month == 12 d = Date.new(year+1, 1, 1) else d = Date.new(year, month+1, 1) end begin d -= 1 end until d.wday == 5 d
end
year = Integer(ARGV.shift) (1..12).each {|month| puts last_friday(year, month)}</lang>
Using the ActiveSupport library for some convenience methods
<lang ruby>require 'rubygems' require 'activesupport'
def last_friday(year, month)
d = Date.new(year, month, 1).end_of_month until d.wday == 5 d = d.yesterday end d
end</lang>
Tcl
<lang tcl>package require Tcl 8.5 set year [lindex $argv 0] foreach dm {02/1 03/1 04/1 05/1 06/1 07/1 08/1 09/1 10/1 11/1 12/1 12/32} {
# The [clock scan] code is unhealthily clever; use it for our own evil purposes set t [clock scan "last friday" -base [clock scan $dm/$year -gmt 1] -gmt 1] # Print the interesting part puts [clock format $t -format "%Y-%m-%d" -gmt 1]
}</lang> Sample execution:
$ tclsh8.5 lastfri.tcl 2012 2012-01-27 2012-02-24 2012-03-30 2012-04-27 2012-05-25 2012-06-29 2012-07-27 2012-08-31 2012-09-28 2012-10-26 2012-11-30 2012-12-28