Initial commit

2022/04/code.go

@@ -0,0 +1,77 @@
+package main
+
+import (
+	"fmt"
+	"log"
+	"strconv"
+	"strings"
+
+	"github.com/jpillora/puzzler/harness/aoc"
+)
+
+func main() {
+	aoc.Harness(run)
+}
+
+func run(part2 bool, input string) any {
+	if input == "" {
+		return "not implemented"
+	}
+	count := 0
+	lines := strings.Split(strings.TrimSpace(input), "\n")
+	for _, line := range lines {
+		pair := strings.SplitN(line, ",", 2)
+		if len(pair) != 2 {
+			log.Panicf("invalid input %q", line)
+		}
+		a := parse(pair[0])
+		b := parse(pair[1])
+		if !part2 && a.subsetEither(b) {
+			count++
+		} else if part2 && a.intersetsEither(b) {
+			count++
+		}
+	}
+	return count
+}
+
+type hilo struct {
+	lo, hi int
+}
+
+func (h hilo) String() string {
+	return fmt.Sprintf("%d-%d", h.lo, h.hi)
+}
+
+func parse(s string) hilo {
+	pair := strings.SplitN(s, "-", 2)
+	if len(pair) != 2 {
+		panic("bad pair")
+	}
+	lo, err := strconv.Atoi(pair[0])
+	if err != nil {
+		panic(err)
+	}
+	hi, err := strconv.Atoi(pair[1])
+	if err != nil {
+		panic(err)
+	}
+	return hilo{lo, hi}
+}
+
+func (a hilo) subsetEither(b hilo) bool {
+	return a.subsetOf(b) || b.subsetOf(a)
+}
+
+func (a hilo) subsetOf(b hilo) bool {
+	return a.lo >= b.lo && a.hi <= b.hi
+}
+
+func (a hilo) intersetsEither(b hilo) bool {
+	return a.intersets(b) || b.intersets(a)
+}
+
+func (a hilo) intersets(b hilo) bool {
+	return a.lo <= b.lo && b.lo <= a.hi || // b.lo in a OR
+		a.lo <= b.hi && b.hi <= a.hi // b.hi in a
+}