change map support for large #'s of snakes (#92)

* change map support for large #'s of snakes

* test square board fn

* format comment

* add whitespace

* better support large #'s of snakes on small boards

* include an intermediate xlarge size

maps/game_map.go

@@ -42,6 +42,19 @@ func AnySize() sizes {
 	return sizes{Dimensions{Width: 0, Height: 0}}
 }
 
+// OddSizes generates square (width = height) board sizes with an odd number of positions
+// in the vertical and horizontal directions.
+// Examples:
+//  - OddSizes(11,21) produces [(11,11), (13,13), (15,15), (17,17), (19,19), (21,21)]
+func OddSizes(min, max uint) sizes {
+	var s sizes
+	for i := min; i <= max; i += 2 {
+		s = append(s, Dimensions{Width: i, Height: i})
+	}
+
+	return s
+}
+
 // FixedSizes creates dimensions for a board that has 1 or more fixed sizes.
 // Examples:
 // - FixedSizes(Dimension{9,11}) supports only a width of 9 and a height of 11.