21st day

Author: majcn

day21/day21.go

@@ -0,0 +1,103 @@
+package main
+
+import (
+	"fmt"
+	"regexp"
+	"strings"
+
+	. "majcn.si/advent-of-code-2022/util"
+)
+
+type Node interface {
+	Value() float64
+}
+
+type ValueNode struct {
+	V float64
+}
+
+func (node *ValueNode) Value() float64 {
+	return node.V
+}
+
+type EquationNode struct {
+	Left     Node
+	Right    Node
+	Function func(left float64, right float64) float64
+}
+
+func (node *EquationNode) Value() float64 {
+	return node.Function(node.Left.Value(), node.Right.Value())
+}
+
+type DataType map[string]Node
+
+func parseData(data string) DataType {
+	dataSplit := strings.Split(data, "\n")
+
+	rValueNode := regexp.MustCompile(`^(\w{4}): (\d+)$`)
+	rEquationNode := regexp.MustCompile(`^(\w{4}): (\w{4}) ([+\-*/]) (\w{4})$`)
+
+	result := make(map[string]Node, len(data))
+	for _, line := range dataSplit {
+		match := rValueNode.FindStringSubmatch(line)
+		if match != nil {
+			result[match[1]] = &ValueNode{V: float64(ParseInt(match[2]))}
+		} else {
+			result[line[:4]] = &EquationNode{}
+		}
+	}
+
+	for _, line := range dataSplit {
+		match := rEquationNode.FindStringSubmatch(line)
+		if match != nil {
+			node, _ := result[match[1]].(*EquationNode)
+			node.Left = result[match[2]]
+			node.Right = result[match[4]]
+			switch match[3][0] {
+			case '+':
+				node.Function = func(left float64, right float64) float64 { return left + right }
+			case '-':
+				node.Function = func(left float64, right float64) float64 { return left - right }
+			case '*':
+				node.Function = func(left float64, right float64) float64 { return left * right }
+			case '/':
+				node.Function = func(left float64, right float64) float64 { return left / right }
+			}
+		}
+	}
+
+	return result
+}
+
+func solvePart1(data DataType) (rc int) {
+	return int(data["root"].Value())
+}
+
+func solvePart2(data DataType) (rc int) {
+	rootNode := data["root"].(*EquationNode)
+	right := rootNode.Right.Value()
+
+	a := 0
+	b := MaxInt / 2
+	for {
+		c := (a + b) / 2
+		data["humn"].(*ValueNode).V = float64(c)
+		left := rootNode.Left.Value()
+
+		switch {
+		case left > right:
+			a = c
+		case left < right:
+			b = c
+		default:
+			return c
+		}
+	}
+}
+
+func main() {
+	data := parseData(FetchInputData(21))
+	fmt.Println(solvePart1(data))
+	fmt.Println(solvePart2(data))
+}

day21/day21_test.go

@@ -0,0 +1,31 @@
+package main
+
+import (
+	"os"
+	"testing"
+
+	. "majcn.si/advent-of-code-2022/util"
+)
+
+func ExpectedPart1() int {
+	return 152
+}
+
+func ExpectedPart2() int {
+	return 301
+}
+
+var data DataType
+
+func init() {
+	input, _ := os.ReadFile("../examples/21.txt")
+	data = parseData(string(input))
+}
+
+func TestPart1(t *testing.T) {
+	AssertTestPartX(t, ExpectedPart1(), solvePart1(data))
+}
+
+func TestPart2(t *testing.T) {
+	AssertTestPartX(t, ExpectedPart2(), solvePart2(data))
+}

examples/21.txt

@@ -0,0 +1,15 @@
+root: pppw + sjmn
+dbpl: 5
+cczh: sllz + lgvd
+zczc: 2
+ptdq: humn - dvpt
+dvpt: 3
+lfqf: 4
+humn: 5
+ljgn: 2
+sjmn: drzm * dbpl
+sllz: 4
+pppw: cczh / lfqf
+lgvd: ljgn * ptdq
+drzm: hmdt - zczc
+hmdt: 32