Added part2. Today was stupid, part numbers should have been unique

day-03/part2.go

@@ -0,0 +1,139 @@
+package main
+
+import "fmt"
+import "os"
+import "log"
+import "regexp"
+import "bufio"
+import "strconv"
+import "slices"
+
+//import "strings"
+
+var number_regex = regexp.MustCompile(`\d*`)
+var token_regex = regexp.MustCompile(`\*`)
+
+func parse_line(str string, mapping map[int]int, current_uid int) ([]int, []bool, map[int]int, int) {
+	number_of_characters := len(str)
+
+	ids := make([]int, number_of_characters)
+	tokens := make([]bool, number_of_characters)
+
+	// First parse tokens, much easier.
+	indicies := token_regex.FindAllStringIndex(str, -1)
+
+	for _, index := range indicies {
+		tokens[index[0]] = true
+	}
+
+	// Ids a bit more complex, requires both indicies and values
+	values := number_regex.FindAllString(str, -1)
+	indicies = number_regex.FindAllStringIndex(str, -1)
+
+	for i := 0; i < len(values); i++ {
+		value := values[i]
+		index := indicies[i][0]
+		// Use a UID not a part number because they may appear twice!
+		current_uid++
+		converted_value, _ := strconv.Atoi(value)
+		mapping[current_uid] = converted_value
+
+		// Loop over n, where n is string length
+		for x := 0; x < len(value); x++ {
+			ids[index+x] = current_uid
+		}
+	}
+
+	return ids, tokens, mapping, current_uid
+}
+
+func extract_gear_ratios(tokens [][]bool, values [][]int, mapping map[int]int) int {
+	total_gear_ratios := 0
+
+	number_of_lines := len(tokens)
+	number_of_columns := len(tokens[0])
+
+	for line_index, token_line := range tokens {
+		// Valid part numbers are 'around' the token.
+		for column_index, token_value := range token_line {
+			if !token_value {
+				continue
+			}
+
+			these_mappings := make([]int, 0)
+
+			start_line := max(min(number_of_lines-1, line_index-1), 0)
+			end_line := max(min(number_of_lines-1, line_index+1), 0)
+
+			start_column := max(min(number_of_columns-1, column_index-1), 0)
+			end_column := max(min(number_of_columns-1, column_index+1), 0)
+
+			for line := start_line; line <= end_line; line++ {
+				for column := start_column; column <= end_column; column++ {
+					this_value := values[line][column]
+					if this_value > 0 {
+						if !(slices.Contains(these_mappings, this_value)) {
+							these_mappings = append(these_mappings, this_value)
+						}
+					}
+				}
+			}
+
+			if len(these_mappings) == 2 {
+				total_gear_ratios += mapping[these_mappings[0]] * mapping[these_mappings[1]]
+			}
+		}
+	}
+
+	return total_gear_ratios
+}
+
+func main() {
+	DEBUG := true
+
+	scanner := bufio.NewScanner(os.Stdin)
+
+	raw_input := make([]string, 0)
+
+	for scanner.Scan() {
+		text := scanner.Text()
+
+		raw_input = append(raw_input, text)
+	}
+
+	if scanner.Err() != nil {
+		log.Fatal("No input provided.")
+	}
+
+	number_of_lines := len(raw_input)
+
+	tokens := make([][]bool, number_of_lines)
+	values := make([][]int, number_of_lines)
+	mapping := make(map[int]int)
+	current_uid := 1
+
+	for i, l := range raw_input {
+		values[i], tokens[i], mapping, current_uid = parse_line(l, mapping, current_uid)
+	}
+
+	if DEBUG {
+		fmt.Println("Raw:")
+		for _, v := range raw_input {
+			fmt.Println(v)
+		}
+
+		fmt.Println("Tokens:")
+		for _, v := range tokens {
+			fmt.Println(v)
+		}
+
+		fmt.Println("Values:")
+		for _, v := range values {
+			fmt.Println(v)
+		}
+	}
+
+	gear_ratio := extract_gear_ratios(tokens, values, mapping)
+
+	fmt.Println("Gear ratio: ", gear_ratio)
+}