[2020-12-10] Add solutions for day10

Makefile

@@ -30,6 +30,8 @@ day09:
 	go run main.go day09 input
 
 day10:
+	go run main.go day10 input
+
 day11:
 day12:
 day13:

day10/example.txt

@@ -0,0 +1,11 @@
+16
+10
+15
+5
+1
+11
+7
+19
+6
+12
+4

day10/example2.txt

@@ -0,0 +1,31 @@
+28
+33
+18
+42
+31
+14
+46
+20
+48
+47
+24
+23
+49
+45
+19
+38
+39
+11
+1
+32
+25
+35
+8
+17
+7
+9
+4
+2
+34
+10
+3

day10/input.txt

@@ -0,0 +1,100 @@
+44
+41
+48
+17
+35
+146
+73
+3
+16
+159
+11
+29
+32
+63
+65
+62
+126
+151
+6
+124
+87
+115
+122
+43
+12
+85
+2
+98
+59
+156
+149
+66
+10
+82
+26
+79
+56
+22
+74
+49
+25
+69
+54
+19
+108
+18
+55
+131
+140
+15
+125
+37
+129
+91
+51
+158
+117
+136
+142
+109
+64
+36
+160
+150
+42
+118
+101
+78
+28
+105
+110
+40
+157
+70
+97
+139
+152
+47
+104
+81
+27
+116
+132
+143
+1
+80
+75
+141
+133
+9
+50
+153
+123
+111
+119
+130
+112
+94
+90
+86

day10/parse.go

@@ -0,0 +1,28 @@
+package day10
+
+import (
+	"sort"
+	"strconv"
+
+	"git.elis.nu/etu/aoc2020/utils"
+)
+
+var rows []int
+
+func ParseFile(input string) {
+	// Add zero as start number
+	rows = append(rows, 0)
+
+	// Parse file
+	for _, line := range utils.GetLinesFromFile("day10/" + input + ".txt") {
+		num, _ := strconv.Atoi(line)
+
+		rows = append(rows, num)
+	}
+
+	// Sort the numbers, will always be needed. And is required for calculation of consolues jolt usage below.
+	sort.Ints(rows)
+
+	// Add the consoles jolt usage by taking the last number plus 3
+	rows = append(rows, rows[len(rows)-1]+3)
+}

day10/solve1.go

@@ -0,0 +1,26 @@
+package day10
+
+import (
+	"log"
+)
+
+func Solve1() {
+	count1 := 0
+	count3 := 0
+
+	for key, value := range rows {
+		if key+1 >= len(rows) {
+			break
+		}
+
+		if value+1 == rows[key+1] {
+			count1++
+		}
+
+		if value+3 == rows[key+1] {
+			count3++
+		}
+	}
+
+	log.Printf("2020-12-10.01: Answer: %d\n", count1*count3)
+}

day10/solve2.go

@@ -0,0 +1,41 @@
+package day10
+
+import (
+	"log"
+)
+
+func Solve2() {
+	log.Printf("2020-12-10.02: Answer: %d\n", calc(rows))
+}
+
+func calc(data []int) int {
+	// Some cached answers, these works since we check if they
+	// increment by one when we split up the data below, so if the
+	// chain is a certain length, we know it works.
+	switch len(data) {
+	case 0, 1, 2:
+		return 1
+	case 3:
+		return 2
+	case 4:
+		return 4
+	case 5:
+		return 7
+	}
+
+	// Locate a good place to break the chain in the middle
+	i := 0
+	for i = 0; i < len(data)-1; i++ {
+		if data[i+1] == data[i]+1 {
+			continue
+		}
+
+		break
+	}
+
+	if len(data[:i]) >= 0 {
+		return calc(data[:i+1]) * calc(data[i+1:])
+	}
+
+	return 0
+}

main.go

@@ -13,6 +13,7 @@ import (
 	"git.elis.nu/etu/aoc2020/day07"
 	"git.elis.nu/etu/aoc2020/day08"
 	"git.elis.nu/etu/aoc2020/day09"
+	"git.elis.nu/etu/aoc2020/day10"
 	"git.elis.nu/etu/aoc2020/utils"
 )
 
@@ -48,5 +49,8 @@ func main() {
 
 	case "day09":
 		utils.Perf("2020-12-09", day09.ParseFile, day09.Solve1, day09.Solve2)
+
+	case "day10":
+		utils.Perf("2020-12-10", day10.ParseFile, day10.Solve1, day10.Solve2)
 	}
 }