2016 Update

Task/Five-weekends/Lua/five-weekends.lua

@@ -0,0 +1,30 @@
+local months={"JAN","MAR","MAY","JUL","AUG","OCT","DEC"}
+local daysPerMonth={31+28,31+30,31+30,31,31+30,31+30,0}
+
+function find5weMonths(year)
+  local list={}
+  local startday=((year-1)*365+math.floor((year-1)/4)-math.floor((year-1)/100)+math.floor((year-1)/400))%7
+
+  for i,v in ipairs(daysPerMonth) do
+    if startday==4 then list[#list+1]=months[i] end
+    if i==1 and year%4==0 and year%100~=0 or year%400==0 then
+      startday=startday+1
+    end
+    startday=(startday+v)%7
+  end
+  return list
+end
+
+local cnt_months=0
+local cnt_no5we=0
+
+for y=1900,2100 do
+  local list=find5weMonths(y)
+  cnt_months=cnt_months+#list
+  if #list==0 then
+    cnt_no5we=cnt_no5we+1
+  end
+  print(y.." "..#list..": "..table.concat(list,", "))
+end
+print("Months with 5 weekends: ",cnt_months)
+print("Years without 5 weekends in the same month:",cnt_no5we)