Day 10 solution

ten/navigation.go

@@ -0,0 +1,134 @@
+package ten
+
+import (
+	"bufio"
+	"os"
+	"sort"
+)
+
+var syntaxScores = map[rune]int{
+	')': 3,
+	']': 57,
+	'}': 1197,
+	'>': 25137,
+}
+
+var autoCompleteScores = map[rune]int{
+	'(': 1,
+	'[': 2,
+	'{': 3,
+	'<': 4,
+}
+
+var pairs = map[rune]rune{
+	')': '(',
+	'}': '{',
+	']': '[',
+	'>': '<',
+}
+
+type errorType string
+
+const (
+	corrupted  errorType = "corrupted"
+	incomplete errorType = "incomplete"
+)
+
+type syntaxError struct {
+	line      string
+	symbol    rune
+	violation errorType
+	stack     []rune
+}
+
+type navigation struct {
+	input      []string
+	validInput []string
+	errors     []syntaxError
+}
+
+func (n *navigation) load(filename string) error {
+	file, err := os.Open(filename)
+	if err != nil {
+		return err
+	}
+	defer file.Close()
+	scanner := bufio.NewScanner(file)
+	for scanner.Scan() {
+		n.input = append(n.input, scanner.Text())
+	}
+	return nil
+}
+
+func (n *navigation) parse() {
+	for _, input := range n.input {
+		stack := []rune{}
+		var e *syntaxError
+		for _, r := range input {
+			switch r {
+			case '(', '{', '[', '<':
+				stack = append(stack, r)
+				continue
+			case ')', '}', ']', '>':
+				if len(stack) < 1 || stack[len(stack)-1] != pairs[r] {
+					e = &syntaxError{
+						line:      input,
+						symbol:    r,
+						violation: corrupted,
+					}
+				} else {
+					stack = stack[:len(stack)-1]
+				}
+			}
+
+			if e != nil {
+				break
+			}
+		}
+
+		if e == nil && len(stack) > 0 {
+			e = &syntaxError{
+				line:      input,
+				symbol:    stack[0],
+				violation: incomplete,
+			}
+		}
+
+		if e != nil {
+			e.stack = stack
+			n.errors = append(n.errors, *e)
+		} else {
+			n.validInput = append(n.validInput, input)
+		}
+
+	}
+}
+
+func (n *navigation) syntaxScore() (score int) {
+	for _, e := range n.errors {
+		if e.violation == corrupted {
+			score += syntaxScores[e.symbol]
+		}
+	}
+
+	return score
+}
+
+func (n *navigation) autoCompleteScore() int {
+	scores := []int{}
+	for _, e := range n.errors {
+		if e.violation == incomplete {
+			total := 0
+			for i := len(e.stack) - 1; i >= 0; i-- {
+				total = (total * 5) + autoCompleteScores[e.stack[i]]
+			}
+			scores = append(scores, total)
+		}
+	}
+
+	// Find the middle value
+	sort.Ints(scores)
+	medianIndex := int(len(scores)/2) + 1
+
+	return scores[medianIndex-1]
+}