2021 - Day 10

2021/10/go.mod

@@ -0,0 +1,9 @@
+module AoC/2021/10
+
+require AoC/2021/common v0.0.0
+
+require github.com/joho/godotenv v1.4.0 // indirect
+
+replace AoC/2021/common v0.0.0 => ../common
+
+go 1.17

2021/10/go.sum

@@ -0,0 +1,2 @@
+github.com/joho/godotenv v1.4.0 h1:3l4+N6zfMWnkbPEXKng2o2/MR5mSwTrBih4ZEkkz1lg=
+github.com/joho/godotenv v1.4.0/go.mod h1:f4LDr5Voq0i2e/R5DDNOoa2zzDfwtkZa6DnEwAbqwq4=

2021/10/main.go

@@ -0,0 +1,164 @@
+package main
+
+import (
+	aoc "AoC/2021/common"
+	"bufio"
+	"sort"
+)
+
+func getScoreCorrupted(line string, index int) (int, int) {
+	c := line[index]
+	if !(c == '(' || c == '{' || c == '[' || c == '<') {
+		return 0, index
+	}
+
+	counter := 0
+	for i := index; i < len(line); i++ {
+		found := line[i]
+
+		switch found {
+		case '(', '{', '[', '<':
+			counter++
+		case ')', '}', ']', '>':
+			counter--
+		}
+
+		if counter == 0 {
+			if c == '(' && found == ')' {
+				return 0, i
+			} else if c == '{' && found == '}' {
+				return 0, i
+			} else if c == '[' && found == ']' {
+				return 0, i
+			} else if c == '<' && found == '>' {
+				return  0, i
+			} else {
+				switch found {
+				case ')':
+					return 3, i
+				case ']':
+					return 57, i
+				case '}':
+					return 1197, i
+				case '>':
+					return 25137, i
+				}
+			}
+		}
+
+	}
+
+	return 0, index
+}
+
+func getScoreIncomplete(line string, index int) (bool, int) {
+	c := line[index]
+	if !(c == '(' || c == '{' || c == '[' || c == '<') {
+		return true, 0
+	}
+
+	counter := 0
+	for i := index; i < len(line); i++ {
+		found := line[i]
+
+		switch found {
+		case '(', '{', '[', '<':
+			counter++
+		case ')', '}', ']', '>':
+			counter--
+		}
+
+		if counter == 0 {
+			if c == '(' && found == ')' {
+				break;
+			} else if c == '{' && found == '}' {
+				break
+			} else if c == '[' && found == ']' {
+				break
+			} else if c == '<' && found == '>' {
+				break
+			} else {
+				// Indicate that the line is corrupted
+				return false, 0
+			}
+		}
+	}
+
+	if counter != 0 {
+		switch c {
+		case '(':
+			return true, 1
+		case '[':
+			return true, 2
+		case '{':
+			return true, 3
+		case '<':
+			return true, 4
+		}
+	}
+
+	return true, 0
+}
+
+func main() {
+	challenge := aoc.New(2021, 10)
+
+	challenge.Test(`[({(<(())[]>[[{[]{<()<>>
+[(()[<>])]({[<{<<[]>>(
+{([(<{}[<>[]}>{[]{[(<()>
+(((({<>}<{<{<>}{[]{[]{}
+[[<[([]))<([[{}[[()]]
+[{[{({}]{}}([{[{{{}}([]
+{<[[]]>}<{[{[{[]{()[[[]
+[<(<(<(<{}))><([]([]()
+<{([([[(<>()){}]>(<<{{
+<{([{{}}[<[[[<>{}]]]>[]]`, []int{26397, 288957})
+
+	challenge.Solution(1, func (input *bufio.Scanner) int {
+		score := 0
+		for ln := 0; input.Scan(); ln++ {
+			line := input.Text()
+
+			fi := len(line)
+			fs := 0
+
+			for i := range line {
+				s, index := getScoreCorrupted(line, i)
+				if s != 0 && index < fi {
+					fi = index
+					fs = s
+				}
+			}
+
+			score += fs
+		}
+		return score
+	})
+
+	challenge.Solution(2, func (input *bufio.Scanner) int {
+		var scores []int
+		for ln := 0; input.Scan(); ln++ {
+			line := input.Text()
+
+			score := 0
+			// We need to itterate in reverse because otherwise the multiplication goes in the wrong order
+			for i := len(line)-1; i >= 0; i-- {
+				v, s := getScoreIncomplete(line, i)
+				if !v {
+					score = 0
+					break
+				} else if s > 0 {
+					score *= 5
+					score += s
+				}
+			}
+
+			if score > 0 {
+				scores = append(scores, score)
+			}
+		}
+		sort.Ints(scores)
+
+		return scores[len(scores)/2]
+	})
+}