clean up main

day1.go

@@ -12,7 +12,7 @@ type Day1Input struct {
 	column2 []int64
 }
 
-func day1_parse(lines []string) (*Day1Input, error) {
+func Day1Parse(lines []string) (*Day1Input, error) {
 	column1 := make([]int64, len(lines))
 	column2 := make([]int64, len(lines))
 
@@ -42,8 +42,8 @@ func day1_parse(lines []string) (*Day1Input, error) {
 	return &parsed, nil
 }
 
-func day1_part1(lines []string) (error) {
-	input, err := day1_parse(lines)
+func Day1Part1(lines []string) (error) {
+	input, err := Day1Parse(lines)
 	if err != nil {
 		return err
 	}
@@ -70,8 +70,8 @@ func day1_part1(lines []string) (error) {
 	return nil
 }
 
-func day1_part2(lines []string) (error) {
-	input, err := day1_parse(lines)
+func Day1Part2(lines []string) (error) {
+	input, err := Day1Parse(lines)
 	if err != nil {
 		return err
 	}

day2.go

@@ -0,0 +1,109 @@
+package main
+
+import (
+	"fmt"
+	"strconv"
+	"strings"
+)
+
+type Day2Input [][]int64
+
+func Day2Parse(lines []string) (Day2Input, error) {
+	rows := make([][]int64, len(lines))
+	for i, line := range lines {
+		levelsCount := strings.Count(line, " ") + 1
+		rows[i] = make([]int64, levelsCount)
+
+		for j, level := range strings.Split(line, " ") {
+			number, err := strconv.ParseInt(level, 10, 0)
+			if err != nil {
+				return nil, err
+			}
+
+			rows[i][j] = number
+		}
+	}
+
+	return rows, nil
+}
+
+func absInt(value int64) int64 {
+	if value < 0 {
+		return -value
+	} else {
+		return value
+	}
+}
+
+func Day2IsReportSafe(report []int64) bool {
+	increasing := false
+	decreasing := false
+
+	for i := range len(report)-1 {
+		if report[i+1] >= report[i] {
+			increasing = true
+		}
+		if report[i+1] <= report[i] {
+			decreasing = true
+		}
+		if absInt(report[i+1] - report[i]) >= 4 {
+			return false
+		}
+
+		if increasing && decreasing {
+			return false
+		}
+	}
+
+	return !(increasing && decreasing) && (increasing || decreasing)
+}
+
+func Day2Part1(lines []string) error {
+	input, err := Day2Parse(lines)
+	if err != nil {
+		return err
+	}
+
+	answer := 0
+	for _, row := range input {
+		if Day2IsReportSafe(row) {
+			answer += 1
+		}
+	}
+
+	fmt.Println(answer)
+
+	return nil
+}
+
+func DeleteAtIndex(slice []int64, index int) []int64 {
+	result := make([]int64, len(slice))
+	copy(result, slice)
+	return append(result[:index], result[index+1:]...)
+}
+
+func Day2Part2(lines []string) error {
+	input, err := Day2Parse(lines)
+	if err != nil {
+		return err
+	}
+
+	answer := 0
+	for _, row := range input {
+		if Day2IsReportSafe(row) {
+			answer += 1
+			continue
+		}
+
+		for i := range len(row) {
+			if Day2IsReportSafe(DeleteAtIndex(row, i)) {
+				answer += 1
+				break
+			}
+		}
+	}
+
+	fmt.Println(answer)
+
+	return nil
+}

day3.go

@@ -0,0 +1,142 @@
+package main
+
+import (
+	"strconv"
+	"strings"
+)
+
+type Day3Mul struct {
+	size int
+	number1 int
+	number2 int
+}
+
+func Day3ParseMulInstruction(text string) *Day3Mul {
+	max_length := 0
+	max_length += 4 // mul(
+	max_length += 3 // 999
+	max_length += 1 // ,
+	max_length += 3 // 999
+	max_length += 1 // )
+
+	if len(text) < 4 {
+		return nil
+	}
+
+	if len(text) > max_length {
+		text = text[:max_length]
+	}
+
+	if text[0:4] != "mul(" {
+		return nil
+	}
+
+	comma_index := strings.IndexRune(text, ',')
+	if (comma_index == -1) {
+		return nil
+	}
+
+	closing_index := strings.IndexRune(text, ')')
+	if (closing_index == -1) {
+		return nil
+	}
+
+	number1_text := text[4:comma_index]
+	number2_text := text[(comma_index+1):closing_index]
+
+	number1, err := strconv.ParseUint(number1_text, 10, 0)
+	if err != nil {
+		return nil
+	}
+	if number1 > 999 {
+		return nil
+	}
+
+	number2, err := strconv.ParseUint(number2_text, 10, 0)
+	if err != nil {
+		return nil
+	}
+	if number2 > 999 {
+		return nil
+	}
+
+	inst := Day3Mul{
+		size: closing_index + 1,
+		number1: int(number1),
+		number2: int(number2),
+	}
+
+	return &inst
+}
+
+func Day3Part1(lines []string) error {
+	answer := 0
+
+	for _, line := range lines {
+		cursor := 0
+		for cursor < len(line) {
+			inst := Day3ParseMulInstruction(line[cursor:])
+			if inst != nil {
+				cursor += inst.size
+				answer += inst.number1 * inst.number2
+			} else {
+				cursor += 1
+			}
+		}
+	}
+
+
+	println(answer)
+
+	return nil
+}
+
+func Day3StartsWith(haystack string, needle string) bool {
+	if len(haystack) < len(needle) {
+		return false
+	}
+
+	return haystack[:len(needle)] == needle
+}
+
+func Day3Part2(lines []string) error {
+	answer := 0
+
+	do_inst := "do()"
+	dont_inst := "don't()"
+
+	enabled := true
+	for _, line := range lines {
+		cursor := 0
+		for cursor < len(line) {
+			rest := line[cursor:]
+			if Day3StartsWith(rest, do_inst) {
+				enabled = true
+				cursor += len(do_inst)
+				continue
+			}
+
+			if Day3StartsWith(rest, dont_inst) {
+				enabled = false
+				cursor += len(dont_inst)
+				continue
+			}
+
+			if enabled {
+				inst := Day3ParseMulInstruction(rest)
+				if inst != nil {
+					cursor += inst.size
+					answer += inst.number1 * inst.number2
+					continue
+				}
+			}
+
+			cursor += 1
+		}
+	}
+
+
+	println(answer)
+
+	return nil
+}

day4.go

@@ -0,0 +1,110 @@
+package main
+
+type Day4Offset struct {
+	x int
+	y int
+}
+
+func Day4IsWordValid(lines []string, x int, y int, table []Day4Offset, word string) bool {
+	for i, offset := range table {
+		y := y + offset.y
+		if y < 0 {
+			return false
+		}
+		if y >= len(lines) {
+			return false
+		}
+
+		x := x + offset.x
+		if x < 0 {
+			return false
+		}
+		if x >= len(lines[y]) {
+			return false
+		}
+
+		if lines[y][x] != word[i] {
+			return false
+		}
+	}
+
+	return true
+}
+
+func Day4Part1(lines []string) error {
+	offsetTables := [][]Day4Offset{
+		[]Day4Offset{
+			Day4Offset{ x: 0, y: 0, },
+			Day4Offset{ x: 1, y: 0, },
+			Day4Offset{ x: 2, y: 0, },
+			Day4Offset{ x: 3, y: 0, },
+		},
+		[]Day4Offset{
+			Day4Offset{ x: 0, y: 0, },
+			Day4Offset{ x: 0, y: 1, },
+			Day4Offset{ x: 0, y: 2, },
+			Day4Offset{ x: 0, y: 3, },
+		},
+		[]Day4Offset{
+			Day4Offset{ x: 0, y: 0, },
+			Day4Offset{ x: 1, y: 1, },
+			Day4Offset{ x: 2, y: 2, },
+			Day4Offset{ x: 3, y: 3, },
+		},
+		[]Day4Offset{
+			Day4Offset{ x:  0, y: 0, },
+			Day4Offset{ x: -1, y: 1, },
+			Day4Offset{ x: -2, y: 2, },
+			Day4Offset{ x: -3, y: 3, },
+		},
+	}
+
+	answer := 0
+	for y := range len(lines) {
+		for x := range len(lines[y]) {
+			for _, table := range offsetTables {
+				if Day4IsWordValid(lines, x, y, table, "XMAS") {
+					answer += 1
+				}
+
+				if Day4IsWordValid(lines, x, y, table, "SAMX") {
+					answer += 1
+				}
+			}
+		}
+	}
+
+	println(answer)
+
+	return nil
+}
+
+func Day4Part2(lines []string) error {
+	table1 := []Day4Offset{
+		Day4Offset{ x: 0, y: 0, },
+		Day4Offset{ x: 1, y: 1, },
+		Day4Offset{ x: 2, y: 2, },
+	}
+
+	table2 := []Day4Offset{
+		Day4Offset{ x: 2, y: 0, },
+		Day4Offset{ x: 1, y: 1, },
+		Day4Offset{ x: 0, y: 2, },
+	}
+
+	answer := 0
+	for y := range len(lines) {
+		for x := range len(lines[y]) {
+			diagonal1 := Day4IsWordValid(lines, x, y, table1, "MAS") || Day4IsWordValid(lines, x, y, table1, "SAM")
+			diagonal2 := Day4IsWordValid(lines, x, y, table2, "MAS") || Day4IsWordValid(lines, x, y, table2, "SAM")
+
+			if diagonal1 && diagonal2 {
+				answer += 1
+			}
+		}
+	}
+
+	println(answer)
+
+	return nil
+}

main.go

@@ -12,6 +12,12 @@ func showUsage() {
 	fmt.Printf("Usage: %s <day> <part> [input.txt]\n", os.Args[0])
 }
 
+type DayPartSolver func([]string) error
+type DaySolver struct {
+	day1 DayPartSolver
+	day2 DayPartSolver
+}
+
 func main() {
 	if (len(os.Args) < 3) {
 		showUsage()
@@ -35,11 +41,26 @@ func main() {
 
 	lines := strings.Split(strings.TrimRight(string(contents), "\n"), "\n")
 
-	if day == "1" {
+	solvers := make(map[string]DaySolver)
+	solvers["1"] = DaySolver{ day1: Day1Part1, day2: Day1Part2 }
+	solvers["2"] = DaySolver{ day1: Day2Part1, day2: Day2Part2 }
+	solvers["3"] = DaySolver{ day1: Day3Part1, day2: Day3Part2 }
+	solvers["4"] = DaySolver{ day1: Day4Part1, day2: Day4Part2 }
+
+	solver, ok := solvers[day]
+
+	if ok {
+		var err error
 		if part == "1" {
-			day1_part1(lines)
+			err = solver.day1(lines)
 		} else if part == "2" {
-			day1_part2(lines)
+			err = solver.day1(lines)
 		}
+
+		if err != nil {
+			log.Fatal(err)
+		}
+	} else {
+		log.Fatal("Day not found")
 	}
 }