Day 13

d09/main.go

@@ -69,6 +69,8 @@ func calculateDistances(data []Route) []int {
 	})
 }
 
+// https://pl.wikipedia.org/wiki/Problem_komiwoja%C5%BCera
+// https://en.wikipedia.org/wiki/Travelling_salesman_problem
 func part1(data []Route) int {
 	distances := calculateDistances(data)
 

d13/input.txt

@@ -0,0 +1,56 @@
+Alice would gain 54 happiness units by sitting next to Bob.
+Alice would lose 81 happiness units by sitting next to Carol.
+Alice would lose 42 happiness units by sitting next to David.
+Alice would gain 89 happiness units by sitting next to Eric.
+Alice would lose 89 happiness units by sitting next to Frank.
+Alice would gain 97 happiness units by sitting next to George.
+Alice would lose 94 happiness units by sitting next to Mallory.
+Bob would gain 3 happiness units by sitting next to Alice.
+Bob would lose 70 happiness units by sitting next to Carol.
+Bob would lose 31 happiness units by sitting next to David.
+Bob would gain 72 happiness units by sitting next to Eric.
+Bob would lose 25 happiness units by sitting next to Frank.
+Bob would lose 95 happiness units by sitting next to George.
+Bob would gain 11 happiness units by sitting next to Mallory.
+Carol would lose 83 happiness units by sitting next to Alice.
+Carol would gain 8 happiness units by sitting next to Bob.
+Carol would gain 35 happiness units by sitting next to David.
+Carol would gain 10 happiness units by sitting next to Eric.
+Carol would gain 61 happiness units by sitting next to Frank.
+Carol would gain 10 happiness units by sitting next to George.
+Carol would gain 29 happiness units by sitting next to Mallory.
+David would gain 67 happiness units by sitting next to Alice.
+David would gain 25 happiness units by sitting next to Bob.
+David would gain 48 happiness units by sitting next to Carol.
+David would lose 65 happiness units by sitting next to Eric.
+David would gain 8 happiness units by sitting next to Frank.
+David would gain 84 happiness units by sitting next to George.
+David would gain 9 happiness units by sitting next to Mallory.
+Eric would lose 51 happiness units by sitting next to Alice.
+Eric would lose 39 happiness units by sitting next to Bob.
+Eric would gain 84 happiness units by sitting next to Carol.
+Eric would lose 98 happiness units by sitting next to David.
+Eric would lose 20 happiness units by sitting next to Frank.
+Eric would lose 6 happiness units by sitting next to George.
+Eric would gain 60 happiness units by sitting next to Mallory.
+Frank would gain 51 happiness units by sitting next to Alice.
+Frank would gain 79 happiness units by sitting next to Bob.
+Frank would gain 88 happiness units by sitting next to Carol.
+Frank would gain 33 happiness units by sitting next to David.
+Frank would gain 43 happiness units by sitting next to Eric.
+Frank would gain 77 happiness units by sitting next to George.
+Frank would lose 3 happiness units by sitting next to Mallory.
+George would lose 14 happiness units by sitting next to Alice.
+George would lose 12 happiness units by sitting next to Bob.
+George would lose 52 happiness units by sitting next to Carol.
+George would gain 14 happiness units by sitting next to David.
+George would lose 62 happiness units by sitting next to Eric.
+George would lose 18 happiness units by sitting next to Frank.
+George would lose 17 happiness units by sitting next to Mallory.
+Mallory would lose 36 happiness units by sitting next to Alice.
+Mallory would gain 76 happiness units by sitting next to Bob.
+Mallory would lose 34 happiness units by sitting next to Carol.
+Mallory would gain 37 happiness units by sitting next to David.
+Mallory would gain 40 happiness units by sitting next to Eric.
+Mallory would gain 18 happiness units by sitting next to Frank.
+Mallory would gain 7 happiness units by sitting next to George.

d13/main.go

@@ -0,0 +1,79 @@
+package main
+
+import (
+	"aoc2015/util"
+	"maps"
+	"regexp"
+	"slices"
+)
+
+func calculateMaxHappiness(data map[string]map[string]int) int {
+	people := slices.Collect(maps.Keys(data))
+	permutations := util.Permutations(people)
+
+	happiness := util.ArrayMap(permutations, func(permutation []string) int {
+		total := 0
+
+		for index, person := range permutation {
+			indexLeft, indexRight := util.NeighborIndexes(index, len(permutation))
+			neighborLeft := permutation[indexLeft]
+			neighborRight := permutation[indexRight]
+			leftHappiness := data[person][neighborLeft]
+			rightHappines := data[person][neighborRight]
+
+			total += leftHappiness + rightHappines
+		}
+
+		return total
+	})
+
+	return slices.Max(happiness)
+}
+
+func part1(data map[string]map[string]int) int {
+	return calculateMaxHappiness(data)
+}
+
+func part2(data map[string]map[string]int) int {
+	people := slices.Collect(maps.Keys(data))
+	data["Me"] = map[string]int{}
+
+	for _, person := range people {
+		data["Me"][person] = 0
+	}
+
+	return calculateMaxHappiness(data)
+}
+
+func main() {
+	lineRegex := regexp.MustCompile(`^([a-zA-Z]+) [a-zA-Z ]+(gain|lose) (\d+) [a-z ]+(\w+).$`)
+	reader := func(name string) map[string]map[string]int {
+		lines := util.ReadLines(name)
+		mappings := map[string]map[string]int{}
+
+		for _, line := range lines {
+			match := lineRegex.FindStringSubmatch(line)
+
+			var value int
+			if match[2] == "gain" {
+				value = util.StringToInt(match[3])
+			} else {
+				value = util.StringToInt(match[3]) * -1
+			}
+
+			person := match[1]
+			neighbor := match[4]
+
+			if _, ok := mappings[person]; !ok {
+				mappings[person] = map[string]int{}
+			}
+
+			mappings[person][neighbor] = value
+		}
+
+		return mappings
+	}
+
+	util.TestRuns("13", reader, part1, part2)
+	util.SolutionRuns("13", reader, part1, part2)
+}

d13/test-runs/0.txt

@@ -0,0 +1,12 @@
+Alice would gain 54 happiness units by sitting next to Bob.
+Alice would lose 79 happiness units by sitting next to Carol.
+Alice would lose 2 happiness units by sitting next to David.
+Bob would gain 83 happiness units by sitting next to Alice.
+Bob would lose 7 happiness units by sitting next to Carol.
+Bob would lose 63 happiness units by sitting next to David.
+Carol would lose 62 happiness units by sitting next to Alice.
+Carol would gain 60 happiness units by sitting next to Bob.
+Carol would gain 55 happiness units by sitting next to David.
+David would gain 46 happiness units by sitting next to Alice.
+David would lose 7 happiness units by sitting next to Bob.
+David would gain 41 happiness units by sitting next to Carol.

util/array.go

@@ -21,3 +21,21 @@ func ArrayFilter[T any](sequence []T, predicate func(T) bool) []T {
 
 	return data
 }
+
+func NeighborIndexes(index int, sequenceLength int) (leftIndex int, rightIndex int) {
+	var indexLeft, indexRight int
+
+	if index-1 < 0 {
+		indexLeft = sequenceLength - 1
+	} else {
+		indexLeft = index - 1
+	}
+
+	if index+1 > sequenceLength-1 {
+		indexRight = 0
+	} else {
+		indexRight = index + 1
+	}
+
+	return indexLeft, indexRight
+}

util/combinatorics.go

@@ -13,3 +13,35 @@ func Doubles[T any](set []T) (subsets [][]T) {
 
 	return result
 }
+
+// Returns all permutations of a given array
+func Permutations[T any](array []T) (permutations [][]T) {
+	var helper func([]T, int)
+	res := [][]T{}
+
+	helper = func(arr []T, n int) {
+		if n == 1 {
+			tmp := make([]T, len(arr))
+			copy(tmp, arr)
+			res = append(res, tmp)
+		} else {
+			for i := 0; i < n; i++ {
+				helper(arr, n-1)
+
+				if n%2 == 1 {
+					tmp := arr[i]
+					arr[i] = arr[n-1]
+					arr[n-1] = tmp
+				} else {
+					tmp := arr[0]
+					arr[0] = arr[n-1]
+					arr[n-1] = tmp
+				}
+			}
+		}
+	}
+
+	helper(array, len(array))
+
+	return res
+}