day3, part2

.gitignore

@@ -1 +1,2 @@
 /.direnv/
+/.go

day3/day-three.go

@@ -0,0 +1,163 @@
+package day3
+
+import (
+	"fmt"
+	"os"
+	"strings"
+	"unicode"
+)
+
+func Run() int {
+	filename := "day3/input"
+	bytes, err := os.ReadFile(filename)
+	if err != nil {
+		panic(fmt.Sprint(err, filename))
+	}
+
+	text := string(bytes)
+	matrix := ReadMatrix(text)
+
+	fmt.Println(matrix.String())
+
+	numbers := ReadNumbers(&matrix)
+	for _, num := range numbers {
+		fmt.Println(num)
+	}
+
+	// partNumbersSum := 0
+	// for _, num := range numbers {
+	// 	if len(num.Specials) > 0 {
+	// 		partNumbersSum += num.Num
+	// 	}
+	// }
+
+	gearRatiosSum := partTwo(numbers)
+
+	return gearRatiosSum
+}
+
+type Matrix [][]rune
+
+func ReadMatrix(text string) Matrix {
+	text = strings.TrimSpace(text)
+	lines := strings.Split(text, "\n")
+	matrix := make([][]rune, len(lines))
+
+	for i, lineStr := range strings.Split(text, "\n") {
+		for _, r := range lineStr {
+			matrix[i] = append(matrix[i], r)
+		}
+	}
+
+	return matrix
+}
+
+func (m *Matrix)String() string {
+	res := make([]string, len(*m))
+	for _, row := range *m {
+		res = append(res, string(row) + "\n")
+	}
+
+	return strings.Join(res, "")
+}
+
+// and now from matrix, i want to scan top-down, left-right
+// when encountering digit - start new number, read it in
+// and when finished reading : scan around for the special symbols
+
+type SpecialSymbol struct {
+	Symb rune
+	X, Y int
+}
+func (s SpecialSymbol) String() string {
+	return fmt.Sprintf("('%s' at x:%d,y:%d)", string(s.Symb), s.X, s.Y)
+}
+func (s SpecialSymbol) Equal() bool {
+	return false
+}
+
+type MatrixNumber struct {
+	Num int
+	Specials map[SpecialSymbol]any
+}
+
+func ReadNumbers(m *Matrix) []MatrixNumber {
+	res := make([]MatrixNumber, 0)
+
+	var curNum *MatrixNumber
+	for x, row := range *m {
+		for y, symb := range row {
+			if unicode.IsDigit(symb) {
+				digit := int(symb - '0')
+				// seing digit
+				if curNum == nil {
+					curNum = &MatrixNumber{
+						Num: digit,
+						Specials: make(map[SpecialSymbol]any),
+					}
+				} else {
+					curNum.Num = curNum.Num*10 + digit
+				}
+
+				// on each digit - scan around for special symbols
+				for i := x-1; i <= x+1; i++ {
+					for j := y-1; j <= y+1; j++ {
+						if isValidCoord(i, j, m) {
+							checkingForSpecial := (*m)[i][j]
+							if checkingForSpecial != '.' && !unicode.IsDigit(checkingForSpecial) {
+								special := SpecialSymbol{
+									Symb: checkingForSpecial,
+									X: i,
+									Y: j,
+								}
+								curNum.Specials[special] = struct{}{}
+							}
+						}
+					}
+				}
+
+				// now let's check for special symbols around and save them
+			}
+			if !unicode.IsDigit(symb) {
+				if curNum != nil {
+					res = append(res, *curNum)
+					curNum = nil
+				}
+			}
+		}
+	}
+
+	return res
+}
+
+// x is row, y is column. from top-left to bottom-right
+func isValidCoord(x, y int, m *Matrix) bool {
+	if x < 0 || y < 0 || x >= len(*m) || y >= len((*m)[x]) {
+		return false
+	}
+	return true
+}
+
+// part 2 - find all gears '*' that connect exactly two numbers
+// multiply the numbers and calculate total sum
+// i guess i could do full scan of my numbers?
+// every time i encounter '*' in special symbols, could put that into map, hopefully?
+// with value for the number
+
+func partTwo(numbers []MatrixNumber) int {
+	res := 0
+	specialsMap := make(map[SpecialSymbol][]MatrixNumber)
+	for _, num := range numbers {
+		for special, _ := range num.Specials {
+			specialsMap[special] = append(specialsMap[special], num)
+		}
+	}
+
+	for special, nums := range specialsMap {
+		if special.Symb == '*' && len(nums) == 2 {
+			res += nums[0].Num * nums[1].Num
+		}
+	}
+
+	return res
+}

day3/example

@@ -0,0 +1,10 @@
+467..114..
+...*......
+..35..633.
+......#...
+617*......
+.....+.58.
+..592.....
+......755.
+...$.*....
+.664.598..

day3/input

@@ -0,0 +1,140 @@
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main.go

@@ -3,11 +3,11 @@ package main
 import (
 	"log"
 
-	"sunshine.industries/aoc2023/day2"
+	"sunshine.industries/aoc2023/day3"
 )
 
 func main() {
 	log.Print("> starting run:")
-	result := day2.Run()
+	result := day3.Run()
-	log.Printf("day2 result: %d", result)
+	log.Printf("day3 result: %d", result)
 }