2016-day20: did an unnecessary merge ranges

2016/day20/main.go

@@ -0,0 +1,63 @@
+package main
+
+import (
+	"flag"
+	"fmt"
+	"math"
+	"sort"
+	"strings"
+
+	"github.com/alexchao26/advent-of-code-go/mathutil"
+	"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 := firewall(util.ReadFile("./input.txt"), part)
+	fmt.Println("Output:", ans)
+}
+
+func firewall(input string, part int) int {
+	var allBlockedRanges [][2]int
+	for _, line := range strings.Split(input, "\n") {
+		var r [2]int
+		fmt.Sscanf(line, "%d-%d", &r[0], &r[1])
+		allBlockedRanges = append(allBlockedRanges, r)
+	}
+	sort.Slice(allBlockedRanges, func(i, j int) bool {
+		if allBlockedRanges[i][0] != allBlockedRanges[j][0] {
+			return allBlockedRanges[i][0] < allBlockedRanges[j][0]
+		}
+		return allBlockedRanges[i][1] < allBlockedRanges[j][1]
+	})
+
+	// merge allBlockedRanges
+	merged := [][2]int{[2]int{}}
+	for _, r := range allBlockedRanges {
+		endOfLastRange := merged[len(merged)-1][1]
+		if endOfLastRange >= r[0]-1 {
+			merged[len(merged)-1][1] = mathutil.MaxInt(endOfLastRange, r[1])
+		} else {
+			merged = append(merged, r)
+		}
+	}
+
+	if part == 1 {
+		return merged[0][1] + 1
+	}
+
+	if merged[len(merged)-1][1] != math.MaxUint32 {
+		merged = append(merged, [2]int{math.MaxUint32, 0})
+	}
+
+	var totalAllowed int
+	for i := 1; i < len(merged); i++ {
+		totalAllowed += merged[i][0] - merged[i-1][1] - 1
+	}
+
+	return totalAllowed
+}

2016/day20/main_test.go

@@ -0,0 +1,31 @@
+package main
+
+import (
+	"testing"
+
+	"github.com/alexchao26/advent-of-code-go/util"
+)
+
+var example = `5-8
+0-2
+4-7`
+
+func Test_firewall(t *testing.T) {
+	tests := []struct {
+		name  string
+		input string
+		part  int
+		want  int
+	}{
+		{"example part1", example, 1, 3},
+		{"actual part1", util.ReadFile("input.txt"), 1, 23923783},
+		{"actual part2", util.ReadFile("input.txt"), 2, 125},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			if got := firewall(tt.input, tt.part); got != tt.want {
+				t.Errorf("firewall() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}