June 2018 Update

Task/Five-weekends/Julia/five-weekends.julia

@@ -1,26 +1,21 @@
-isdefined(:Date) || using Dates
+isweekend(dt::Date) = Dates.dayofweek(dt) ∈ (Dates.Friday, Dates.Saturday, Dates.Sunday)
 
-const wday = Dates.Fri
-const lo = 1900
-const hi = 2100
-const showres = 5
-
-mfive = recur(Date(lo, 1):Month(1):Date(hi, 12)) do m
-    Dates.daysinmonth(m) == 31 && Dates.dayofweek(m) == wday
+function hasfiveweekend(month::Integer, year::Integer)
+    dmin = Date(year, month, 1)
+    dmax = dmin + Dates.Day(Dates.daysinmonth(dmin) - 1)
+    return count(isweekend, dmin:dmax) ≥ 15
 end
 
-println("Considering the years from ", lo, " to ", hi, ".\n")
-println("There are ", length(mfive), " months having 5 3-day weekends.")
+months = collect((y, m) for y in 1900:2100, m in 1:12 if hasfiveweekend(m, y))
 
-println("The first ", showres, " such months are:")
-for m in mfive[1:showres]
-    println("    ", Dates.monthname(m), " ", Dates.year(m))
-end
+println("Number of months with 5 full-weekends: $(length(months))")
+println("First five such months:")
+for (y, m) in months[1:5] println(" - $y-$m") end
+println("Last five such months:")
+for (y, m) in months[end-4:end] println(" - $y-$m") end
 
-println("\nThe last ", showres, " such months are:")
-for m in mfive[end-showres+1:end]
-    println("    ", Dates.monthname(m), " ", Dates.year(m))
-end
+# extra credit
+yrs = getindex.(months, 1)
+nyrs = 2100 - 1899 - length(unique(yrs))
 
-print("\nThere are ", length(filter(y -> !(y in year(mfive)), lo:hi)))
-println(" years that have no such months.")
+println("Number of year with not one 5-full-weekend month: $nyrs")