2023-19 not the prettiest recursion...

2023/day19/main.go

@@ -0,0 +1,240 @@
+package main
+
+import (
+	_ "embed"
+	"flag"
+	"fmt"
+	"strings"
+
+	"github.com/alexchao26/advent-of-code-go/cast"
+	"github.com/alexchao26/advent-of-code-go/util"
+)
+
+//go:embed input.txt
+var input string
+
+func init() {
+	// do this in init (not main) so test file has same input
+	input = strings.TrimRight(input, "\n")
+	if len(input) == 0 {
+		panic("empty input.txt file")
+	}
+}
+
+func main() {
+	var part int
+	flag.IntVar(&part, "part", 1, "part 1 or 2")
+	flag.Parse()
+	fmt.Println("Running part", part)
+
+	if part == 1 {
+		ans := part1(input)
+		util.CopyToClipboard(fmt.Sprintf("%v", ans))
+		fmt.Println("Output:", ans)
+	} else {
+		ans := part2(input)
+		util.CopyToClipboard(fmt.Sprintf("%v", ans))
+		fmt.Println("Output:", ans)
+	}
+}
+
+func part1(input string) int {
+	parts, workflowsMap := parseInput(input)
+
+	ans := 0
+
+	for _, p := range parts {
+		currentWorkflowName := "in"
+		for currentWorkflowName != "A" && currentWorkflowName != "R" {
+			wf := workflowsMap[currentWorkflowName]
+			for _, rule := range wf.ruleStrings {
+				if !strings.Contains(rule, ":") {
+					currentWorkflowName = rule
+					break
+				}
+
+				colonSplit := strings.Split(rule, ":")
+				output := colonSplit[1]
+
+				if strings.Contains(colonSplit[0], "<") {
+					conditionalParts := strings.Split(colonSplit[0], "<")
+					if p[conditionalParts[0]] < cast.ToInt(conditionalParts[1]) {
+						currentWorkflowName = output
+						break
+					}
+				} else if strings.Contains(colonSplit[0], ">") {
+					conditionalParts := strings.Split(colonSplit[0], ">")
+					if p[conditionalParts[0]] > cast.ToInt(conditionalParts[1]) {
+						currentWorkflowName = output
+						break
+					}
+				} else {
+					panic("unexpected workflow rule conditional: " + rule)
+				}
+			}
+		}
+
+		if currentWorkflowName == "A" {
+			ans += p.sumRatings()
+		}
+	}
+
+	return ans
+}
+
+type part map[string]int
+
+func (p part) sumRatings() int {
+	total := 0
+	for _, v := range p {
+		total += v
+	}
+	return total
+}
+
+type workflow struct {
+	name        string
+	ruleStrings []string
+}
+
+func parseInput(input string) (parts []part, workflowsMap map[string]workflow) {
+	inputParts := strings.Split(input, "\n\n")
+
+	workflowsMap = map[string]workflow{}
+
+	// process workflows
+	for _, line := range strings.Split(inputParts[0], "\n") {
+		lineParts := strings.Split(line, "{")
+		wf := workflow{
+			name:        lineParts[0],
+			ruleStrings: strings.Split(lineParts[1][:len(lineParts[1])-1], ","),
+		}
+		workflowsMap[wf.name] = wf
+	}
+
+	for _, line := range strings.Split(inputParts[1], "\n") {
+		withoutBraces := line[1 : len(line)-1]
+		p := part{}
+		for _, ratingStr := range strings.Split(withoutBraces, ",") {
+			ratingParts := strings.Split(ratingStr, "=")
+			p[ratingParts[0]] = cast.ToInt(ratingParts[1])
+		}
+		parts = append(parts, p)
+	}
+
+	return parts, workflowsMap
+}
+
+func part2(input string) int {
+	_, workflowsMap := parseInput(input)
+
+	// 1 to 4000 bounds for each rating...
+	boundedParts := map[string][2]int{
+		"x": {1, 4000},
+		"m": {1, 4000},
+		"a": {1, 4000},
+		"s": {1, 4000},
+	}
+
+	return updatePartBoundsAndSplit(boundedParts, workflowsMap, "in", 0)
+}
+
+func updatePartBoundsAndSplit(boundedParts map[string][2]int, workflowsMap map[string]workflow, currentWorkflow string, debugDepth int) int {
+	if currentWorkflow == "R" {
+		return 0
+	}
+	if currentWorkflow == "A" {
+		product := 1
+		for _, bounds := range boundedParts {
+			product *= bounds[1] - bounds[0] + 1
+		}
+		return product
+	}
+
+	// split based on rules...
+	total := 0
+
+	// for each rule,
+	// the rule either passes and moves onto a different workflow,
+	// or fails and checks the next rule
+	// need to sum up both forks
+	//
+	// passing is handled via recursion, failing is handled via looping to the next rule
+	// in both cases the bounds need to be updated
+	for _, rule := range workflowsMap[currentWorkflow].ruleStrings {
+		// just the next workflow to go after
+		if !strings.Contains(rule, ":") {
+			nextWorkflowName := rule
+			total += updatePartBoundsAndSplit(boundedParts, workflowsMap, nextWorkflowName, debugDepth+1)
+			break
+		}
+
+		colonSplit := strings.Split(rule, ":")
+		nextWorkflowName := colonSplit[1]
+
+		if strings.Contains(colonSplit[0], "<") {
+			conditionalParts := strings.Split(colonSplit[0], "<")
+			ratingName := conditionalParts[0]
+			ratingTestValue := cast.ToInt(conditionalParts[1])
+
+			// fork the part that passes the < conditional
+			copyOfBounds := copyBoundedPartsMap(boundedParts)
+			copyOfBounds[ratingName] = [2]int{
+				copyOfBounds[ratingName][0],
+				ratingTestValue - 1,
+			}
+			// check that the new bounds are still valid
+			if copyOfBounds[ratingName][0] <= copyOfBounds[ratingName][1] {
+				total += updatePartBoundsAndSplit(copyOfBounds, workflowsMap, nextWorkflowName, debugDepth+1)
+			}
+
+			// second fork for failing the conditional, need to update the boundedParts to fail
+			boundedParts[ratingName] = [2]int{
+				ratingTestValue,
+				boundedParts[ratingName][1],
+			}
+			// check that the new bounds are still valid
+			if boundedParts[ratingName][0] > boundedParts[ratingName][1] {
+				break
+			}
+		} else if strings.Contains(colonSplit[0], ">") {
+			conditionalParts := strings.Split(colonSplit[0], ">")
+			ratingName := conditionalParts[0]
+			ratingTestValue := cast.ToInt(conditionalParts[1])
+
+			// fork the part that passes the > conditional
+			copyOfBounds := copyBoundedPartsMap(boundedParts)
+			copyOfBounds[ratingName] = [2]int{
+				ratingTestValue + 1,
+				copyOfBounds[ratingName][1],
+			}
+
+			// check that the new bounds are still valid before recursing
+			if copyOfBounds[ratingName][0] <= copyOfBounds[ratingName][1] {
+				total += updatePartBoundsAndSplit(copyOfBounds, workflowsMap, nextWorkflowName, debugDepth+1)
+			}
+
+			// second fork for failing the conditional, need to update the boundedParts to fail
+			boundedParts[ratingName] = [2]int{
+				boundedParts[ratingName][0],
+				ratingTestValue,
+			}
+			// check that the new bounds are still valid
+			if boundedParts[ratingName][0] > boundedParts[ratingName][1] {
+				break
+			}
+		} else {
+			panic("unexpected workflow rule conditional: " + rule)
+		}
+	}
+
+	return total
+}
+
+func copyBoundedPartsMap(boundedParts map[string][2]int) map[string][2]int {
+	cp := map[string][2]int{}
+	for k, v := range boundedParts {
+		cp[k] = v
+	}
+	return cp
+}

2023/day19/main_test.go

@@ -0,0 +1,75 @@
+package main
+
+import (
+	"testing"
+)
+
+var example = `px{a<2006:qkq,m>2090:A,rfg}
+pv{a>1716:R,A}
+lnx{m>1548:A,A}
+rfg{s<537:gd,x>2440:R,A}
+qs{s>3448:A,lnx}
+qkq{x<1416:A,crn}
+crn{x>2662:A,R}
+in{s<1351:px,qqz}
+qqz{s>2770:qs,m<1801:hdj,R}
+gd{a>3333:R,R}
+hdj{m>838:A,pv}
+
+{x=787,m=2655,a=1222,s=2876}
+{x=1679,m=44,a=2067,s=496}
+{x=2036,m=264,a=79,s=2244}
+{x=2461,m=1339,a=466,s=291}
+{x=2127,m=1623,a=2188,s=1013}`
+
+func Test_part1(t *testing.T) {
+	tests := []struct {
+		name  string
+		input string
+		want  int
+	}{
+		{
+			name:  "example",
+			input: example,
+			want:  19114,
+		},
+		{
+			name:  "actual",
+			input: input,
+			want:  287054,
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			if got := part1(tt.input); got != tt.want {
+				t.Errorf("part1() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}
+
+func Test_part2(t *testing.T) {
+	tests := []struct {
+		name  string
+		input string
+		want  int
+	}{
+		{
+			name:  "example",
+			input: example,
+			want:  167409079868000,
+		},
+		{
+			name:  "actual",
+			input: input,
+			want:  131619440296497,
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			if got := part2(tt.input); got != tt.want {
+				t.Errorf("part2() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}