move area calculation into a function

fix mustConvHex docstring

day-18/one.go

@@ -1,7 +1,6 @@
 package main
 
 import (
-	"math"
 	"regexp"
 )
 
@@ -26,14 +25,5 @@ func one(lines []string) int {
 	imager := newImager()
 	buildImage(fromRegex, imager, lines)
 
-	area := 0
-	for i := 0; i < len(imager.space); i++ {
-		next := imager.space[(i+1)%len(imager.space)]
-		area += imager.space[i].X*next.Y - imager.space[i].Y*next.X
-	}
-
-	// add perimeter to area within perimeter
-	area = len(imager.space) + (int(math.Abs(float64(area))) / 2)
-
-	return area - len(imager.space)/2 + 1
+	return calculateArea(imager.space)
 }

day-18/two.go

@@ -1,7 +1,6 @@
 package main
 
 import (
-	"math"
 	"strings"
 )
 
@@ -23,14 +22,5 @@ func two(lines []string) int {
 	imager := newImager()
 	buildImage(fromHex, imager, lines)
 
-	area := 0
-	for i := 0; i < len(imager.space); i++ {
-		next := imager.space[(i+1)%len(imager.space)]
-		area += imager.space[i].X*next.Y - imager.space[i].Y*next.X
-	}
-
-	// add perimeter to area within perimeter
-	area = len(imager.space) + (int(math.Abs(float64(area))) / 2)
-
-	return area - len(imager.space)/2 + 1
+	return calculateArea(imager.space)
 }

day-18/util.go

@@ -3,6 +3,7 @@ package main
 import (
 	"bufio"
 	"log"
+	"math"
 	"os"
 	"regexp"
 	"strconv"
@@ -47,7 +48,7 @@ func mustConv(s string) int {
 	return n
 }
 
-// mustConv converts string to int
+// mustConvHex converts a hex string to int
 // it will panic if an error occurs
 func mustConvHex(s string) int {
 	n, err := strconv.ParseInt(s, 16, 64)
@@ -56,3 +57,17 @@ func mustConvHex(s string) int {
 	}
 	return int(n)
 }
+
+// calculateArea returns the area of the polygon described by imager.space
+func calculateArea(space []coords) int {
+	area := 0
+	for i := 0; i < len(space); i++ {
+		next := space[(i+1)%len(space)]
+		area += space[i].X*next.Y - space[i].Y*next.X
+	}
+
+	// add perimeter to area within perimeter
+	area = len(space) + (int(math.Abs(float64(area))) / 2)
+
+	return area - len(space)/2 + 1
+}