2015-day09: traveling salesman/santa

2015/day09/main.go

@@ -0,0 +1,82 @@
+package main
+
+import (
+	"fmt"
+	"math"
+	"strings"
+
+	"github.com/alexchao26/advent-of-code-go/mathutil"
+
+	"github.com/alexchao26/advent-of-code-go/cast"
+	"github.com/alexchao26/advent-of-code-go/util"
+)
+
+func main() {
+	min, max := travelingSalesman(util.ReadFile("./input.txt"))
+	fmt.Printf("Part1: %d\nPart2: %d\n", min, max)
+}
+
+func travelingSalesman(input string) (int, int) {
+	graph := newGraphFromInput(input)
+
+	min := math.MaxInt32
+	max := 0
+	for k := range graph {
+		dfsMin, dfsMax := dfsTotalDistance(graph, k, map[string]bool{k: true})
+		min = mathutil.MinInt(min, dfsMin)
+		max = mathutil.MaxInt(max, dfsMax)
+	}
+
+	return min, max
+}
+
+func dfsTotalDistance(graph mapGraph, entry string, visited map[string]bool) (min, max int) {
+	// if all nodes have been visited, return a zero length
+	if len(visited) == len(graph) {
+		return 0, 0
+	}
+
+	minDistance := math.MaxInt32
+	maxDistance := 0
+
+	for k := range graph {
+		if !visited[k] {
+			visited[k] = true
+
+			weight := graph[entry][k]
+			minRecurse, maxRecurse := dfsTotalDistance(graph, k, visited)
+			minDistance = mathutil.MinInt(minDistance, weight+minRecurse)
+			maxDistance = mathutil.MaxInt(maxDistance, weight+maxRecurse)
+
+			// backtrack
+			// delete to so length of visited is accurate
+			delete(visited, k)
+		}
+	}
+
+	return minDistance, maxDistance
+}
+
+type mapGraph map[string]map[string]int
+
+func newGraphFromInput(input string) (graph mapGraph) {
+	graph = make(mapGraph)
+	for _, line := range strings.Split(input, "\n") {
+		parts := strings.Split(line, " ")
+		start, end := parts[0], parts[2]
+		weight := cast.ToInt(parts[4])
+
+		// ensure nested map exists
+		if graph[start] == nil {
+			graph[start] = make(map[string]int)
+		}
+		if graph[end] == nil {
+			graph[end] = make(map[string]int)
+		}
+
+		// set weight in both directions
+		graph[start][end] = weight
+		graph[end][start] = weight
+	}
+	return graph
+}

2015/day09/main_test.go

@@ -0,0 +1,29 @@
+package main
+
+import (
+	"testing"
+
+	"github.com/alexchao26/advent-of-code-go/util"
+)
+
+func Test_travelingSalesman(t *testing.T) {
+	tests := []struct {
+		name      string
+		input     string
+		wantPart1 int
+		wantPart2 int
+	}{
+		{"actual", util.ReadFile("input.txt"), 117, 909},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			got1, got2 := travelingSalesman(tt.input)
+			if got1 != tt.wantPart1 {
+				t.Errorf("travelingSalesman() part1 = %v, want %v", got1, tt.wantPart1)
+			}
+			if got2 != tt.wantPart2 {
+				t.Errorf("travelingSalesman() part2 = %v, want %v", got2, tt.wantPart2)
+			}
+		})
+	}
+}