Data commit

Task/Five-weekends/Tcl/five-weekends.tcl

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+package require Tcl 8.5
+
+set months {}
+set years {}
+for {set year 1900} {$year <= 2100} {incr year} {
+    set count [llength $months]
+    foreach month {Jan Mar May Jul Aug Oct Dec} {
+	set date [clock scan "$month/01/$year" -format "%b/%d/%Y" -locale en_US]
+	if {[clock format $date -format %u] == 5} {
+	    # Month with 31 days that starts on a Friday => has 5 weekends
+	    lappend months "$month $year"
+	}
+    }
+    if {$count == [llength $months]} {
+	# No change to number of months; year must've been without
+	lappend years $year
+    }
+}
+puts "There are [llength $months] months with five weekends"
+puts [join [list {*}[lrange $months 0 4] ... {*}[lrange $months end-4 end]] \n]
+puts "There are [llength $years] years without any five-weekend months"
+puts [join $years ","]