partial d15

d15/common.go

@@ -0,0 +1,44 @@
+package d15
+
+import (
+	"strconv"
+	"strings"
+)
+
+func weightNeighbors(in string) (weights, neighbors) {
+	weights := make(weights)
+	neighbors := make(neighbors)
+	lines := strings.Split(strings.TrimSpace(in), "\n")
+	height := len(lines)
+	width := len(lines[0])
+	for y, line := range lines {
+		for x, weight := range strings.Split(line, "") {
+			weight, _ := strconv.Atoi(weight)
+			weights[node(x+y*height)] = weight
+		}
+	}
+	maxX := width
+	maxY := height
+	for height >= 0 {
+		width = maxX
+		for width >= 0 {
+			current := node(width + height*maxY)
+			if height > 0 {
+				neighbors[current] = append(neighbors[current], node(width+(height-1)*maxY))
+			}
+			if height < maxY {
+				neighbors[current] = append(neighbors[current], node(width+(height+1)*maxY))
+			}
+			if width > 0 {
+				neighbors[current] = append(neighbors[current], node(width+height*maxY-1))
+			}
+			if width < maxX {
+				neighbors[current] = append(neighbors[current], node(width+height*maxY+1))
+
+			}
+			width--
+		}
+		height--
+	}
+	return weights, neighbors
+}

d15/d15_test.go

@@ -0,0 +1,51 @@
+package d15
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestP1(t *testing.T) {
+	result := P1(`1163751742
+1381373672
+2136511328
+3694931569
+7463417111
+1319128137
+1359912421
+3125421639
+1293138521
+2311944581`)
+
+	assert.EqualValues(t, 40, result)
+}
+
+func TestP2(t *testing.T) {
+	result := P2(`1163751742
+1381373672
+2136511328
+3694931569
+7463417111
+1319128137
+1359912421
+3125421639
+1293138521
+2311944581`)
+
+	assert.EqualValues(t, 315, result)
+}
+
+func BenchmarkP2(t *testing.B) {
+	P2(`1163751742
+1381373672
+2136511328
+3694931569
+7463417111
+1319128137
+1359912421
+3125421639
+1293138521
+2311944581`)
+
+}

d15/dijkstra.go

@@ -0,0 +1,58 @@
+package d15
+
+import (
+	"math"
+
+	"golang.org/x/exp/maps"
+)
+
+type node int
+
+type weights map[node]int
+
+type neighbors map[node][]node
+
+func minDistance(unvisited weights, distances weights) node {
+	var min node
+	var minDistance = math.MaxInt64
+	for current := range unvisited {
+		if distances[current] < minDistance {
+			min = current
+			minDistance = distances[current]
+		}
+	}
+
+	return min
+}
+
+func assignMap[M ~map[K]V, K comparable, V any](m M, v V) M {
+	n := make(M, len(m))
+	for k := range m {
+		n[k] = v
+	}
+	return n
+
+}
+
+func dijkstra(start node, end node, weights weights, neighbors neighbors) int {
+	distances := assignMap(weights, math.MaxInt64)
+	unvisited := maps.Clone(weights)
+
+	distances[start] = 0
+
+	for len(unvisited) != 0 {
+		current := minDistance(unvisited, distances)
+
+		delete(unvisited, current)
+
+		for _, neighbor := range neighbors[current] {
+			oldDistance := distances[neighbor]
+			newDistance := weights[neighbor] + distances[current]
+			if newDistance < oldDistance {
+				distances[neighbor] = newDistance
+			}
+		}
+	}
+
+	return distances[end]
+}

d15/dijkstra_test.go

@@ -0,0 +1,7 @@
+package d15
+
+import "testing"
+
+func TestDijkstra(t *testing.T) {
+
+}

d15/p1.go

@@ -0,0 +1,6 @@
+package d15
+
+func P1(in string) int {
+	weights, neighbors := weightNeighbors(in)
+	return dijkstra(0, node(len(weights)-1), weights, neighbors)
+}

d15/p2.go

@@ -0,0 +1,61 @@
+package d15
+
+import (
+	"fmt"
+	"strconv"
+	"strings"
+)
+
+func expand(in [][]int) [][]int {
+	height := len(in)
+	width := len(in[0])
+
+	expanded := make([][]int, height*5)
+
+	for y := range expanded {
+		expanded[y] = make([]int, width*5)
+	}
+
+	for y, line := range in {
+		for x, num := range line {
+			for i := 0; i < 5; i++ {
+				for j := 0; j < 5; j++ {
+					expanded[y+(height*i)][x+(width*j)] = (num + i + j) % 9
+				}
+			}
+		}
+	}
+
+	return expanded
+}
+
+func expandMap(in string) string {
+	lines := make([][]int, 0)
+	for _, line := range strings.Split(strings.TrimSpace(in), "\n") {
+		nums := make([]int, 0)
+		for _, weight := range strings.Split(line, "") {
+			weight, _ := strconv.Atoi(weight)
+			nums = append(nums, weight)
+		}
+		lines = append(lines, nums)
+	}
+
+	expanded := expand(lines)
+
+	newMap := ""
+
+	for _, line := range expanded {
+		for _, num := range line {
+			newMap = newMap + fmt.Sprint(num)
+		}
+
+		newMap += "\n"
+	}
+
+	return newMap
+}
+
+func P2(in string) int {
+	weights, neighbors := weightNeighbors(expandMap(in))
+	return dijkstra(0, node(len(weights)-1), weights, neighbors)
+}