2016-day03: validating triangle lengths

2016/day03/main.go

@@ -0,0 +1,73 @@
+package main
+
+import (
+	"flag"
+	"fmt"
+	"regexp"
+	"strings"
+
+	"github.com/alexchao26/advent-of-code-go/util"
+)
+
+func main() {
+	var part int
+	flag.IntVar(&part, "part", 1, "part 1 or 2")
+	flag.Parse()
+	fmt.Println("Running part", part)
+
+	ans := countValidTriangles(util.ReadFile("./input.txt"), part)
+	fmt.Println("Output:", ans)
+}
+
+func countValidTriangles(input string, part int) int {
+	triangleEdges := parseInput(input)
+
+	if part == 2 {
+		triangleEdges = transformTriangles(triangleEdges)
+	}
+
+	var valid int
+	for _, tri := range triangleEdges {
+		// lazy, just check the three scenarios
+		if tri[0]+tri[1] <= tri[2] {
+			continue
+		}
+		if tri[0]+tri[2] <= tri[1] {
+			continue
+		}
+		if tri[1]+tri[2] <= tri[0] {
+			continue
+		}
+		valid++
+	}
+
+	return valid
+}
+
+var multipleSpaces = regexp.MustCompile("[\\s]{2,}")
+
+func parseInput(input string) (ans [][3]int) {
+	lines := strings.Split(input, "\n")
+	for _, l := range lines {
+		l = multipleSpaces.ReplaceAllString(l, " ")
+		var triangleEdges [3]int
+		fmt.Sscanf(l, " %d %d %d", &triangleEdges[0], &triangleEdges[1], &triangleEdges[2])
+		ans = append(ans, triangleEdges)
+	}
+	return ans
+}
+
+// for part 2 where rows are in columns of 3 for some stupid reason
+func transformTriangles(triangles [][3]int) [][3]int {
+	var newTriangles [][3]int
+	for i := 0; i < len(triangles); i += 3 {
+		for col := 0; col < 3; col++ {
+			var edge [3]int
+			for row := 0; row < 3; row++ {
+				edge[row] = triangles[i+row][col]
+			}
+			newTriangles = append(newTriangles, edge)
+		}
+	}
+	return newTriangles
+}