2023 Day 3 Complete!

2023/day03/main.go

@@ -0,0 +1,110 @@
+package main
+
+import (
+	"fmt"
+
+	h "git.bullercodeworks.com/brian/adventofcode/helpers"
+)
+
+func main() {
+	inp := h.StdinToStringSlice()
+	part1(inp)
+	part2(inp)
+}
+
+func part1(input []string) {
+	bm := h.StringSliceToCoordByteMap(input)
+	symbols := bm.FindAllNot('0', '1', '2', '3', '4', '5', '6', '7', '8', '9', '.')
+	// Gather a list of numbers that are adjacent to the symbols
+	nums := make(map[h.Coordinate]int)
+	for k, _ := range symbols {
+		wrk := findPartNumsFrom(bm, k)
+		for coord, val := range wrk {
+			nums[coord] = val
+		}
+	}
+	var sum int
+	for _, v := range nums {
+		sum += v
+	}
+	fmt.Println("# Part 1")
+	fmt.Println(sum)
+}
+
+func part2(input []string) {
+	bm := h.StringSliceToCoordByteMap(input)
+	maybeGears := bm.FindAll('*')
+	var ratioSum int
+	for _, k := range maybeGears {
+		wrk := findPartNumsFrom(bm, k)
+		if len(wrk) != 2 {
+			// It's not a gear
+			continue
+		}
+		var second bool
+		var ratio int
+		for _, v := range wrk {
+			if !second {
+				ratio += v
+				second = true
+			} else {
+				ratio *= v
+			}
+		}
+		ratioSum += ratio
+	}
+	fmt.Println("# Part 2")
+	fmt.Println(ratioSum)
+}
+
+func findPartNumsFrom(m h.CoordByteMap, c h.Coordinate) map[h.Coordinate]int {
+	partNums := make(map[h.Coordinate]int)
+	for _, chk := range []h.Coordinate{
+		c.North(),
+		c.NE(),
+		c.East(),
+		c.SE(),
+		c.South(),
+		c.SW(),
+		c.West(),
+		c.NW(),
+	} {
+		if m.Get(chk) >= '0' && m.Get(chk) <= '9' {
+			v, pos := parseNumAt(m, chk)
+			partNums[pos] = v
+		}
+	}
+	return partNums
+}
+
+// parseNumAt returns the number at c and the Coordinate
+// that the first digit of that number is at
+func parseNumAt(m h.CoordByteMap, c h.Coordinate) (int, h.Coordinate) {
+	var resStr string
+	startCoord := c
+	// From 'c' move left until we find the first digit
+	chk := m.Get(startCoord)
+	for coordIsNum(m, startCoord) {
+		startCoord = startCoord.West()
+		chk = m.Get(startCoord)
+	}
+	startCoord = startCoord.East()
+
+	// Now put the number at 'startCoord' together
+	parseNum := startCoord
+	chk = m.Get(startCoord)
+	for coordIsNum(m, parseNum) {
+		resStr = fmt.Sprintf("%s%s", resStr, string(chk))
+		parseNum = parseNum.East()
+		chk = m.Get(parseNum)
+	}
+	if resStr == "" {
+		return -1, h.Coordinate{X: -1, Y: -1}
+	}
+	return h.Atoi(resStr), startCoord
+}
+
+func coordIsNum(m h.CoordByteMap, c h.Coordinate) bool {
+	wrk := m.Get(c)
+	return wrk >= '0' && wrk <= '9'
+}