2018 day06 solution, patch 2020 scripts missing flag.Parse()

2018/day06/main.go

@@ -0,0 +1,132 @@
+package main
+
+import (
+	"flag"
+	"fmt"
+	"math"
+	"strings"
+
+	"github.com/alexchao26/advent-of-code-go/util"
+)
+
+func main() {
+	var part int
+	flag.IntVar(&part, "part", 1, "part 1 or 2")
+	flag.Parse()
+	fmt.Println("Running part", part)
+
+	if part == 1 {
+		ans := part1(util.ReadFile("./input.txt"))
+		fmt.Println("Output:", ans)
+	} else {
+		ans := part2(util.ReadFile("./input.txt"), 10000)
+		fmt.Println("Output:", ans)
+	}
+}
+
+func part1(input string) int {
+	coords := parseInputCoords(input)
+
+	boundLeft, boundRight, boundTop, boundBottom := getBounds(coords)
+
+	// maps coordinates to the number (count) of cells that they are closest too
+	coordsToMinDistanceCounts := map[[2]int]int{}
+
+	for r := boundTop; r <= boundBottom; r++ {
+		for c := boundLeft; c <= boundRight; c++ {
+			bestManhattan := math.MaxInt16
+			var coordsToBest [2]int
+			distCounts := map[int]int{} // dedeupe equidistant cells
+			for _, coord := range coords {
+				man := util.ManhattanDistance(r, c, coord[0], coord[1])
+				if man <= bestManhattan {
+					bestManhattan = man
+					coordsToBest = coord
+					distCounts[bestManhattan]++
+				}
+			}
+
+			// do not increment anything if there were two equidistant coords
+			if distCounts[bestManhattan] == 1 {
+				coordsToMinDistanceCounts[coordsToBest]++
+			}
+		}
+	}
+
+	var largest int
+	for coord, val := range coordsToMinDistanceCounts {
+		// exclude edges
+		if coord[0] == boundTop || coord[0] == boundBottom {
+			continue
+		}
+		if coord[1] == boundLeft || coord[1] == boundRight {
+			continue
+		}
+
+		if val > largest {
+			largest = val
+		}
+	}
+	return largest
+}
+
+func part2(input string, dist int) int {
+	coords := parseInputCoords(input)
+
+	boundLeft, boundRight, boundTop, boundBottom := getBounds(coords)
+
+	coordsToTotalDist := map[[2]int]int{}
+	var area int
+	for r := boundTop; r <= boundBottom; r++ {
+		for c := boundLeft; c <= boundRight; c++ {
+			point := [2]int{r, c}
+			for _, coord := range coords {
+				coordsToTotalDist[point] += util.ManhattanDistance(point[0], point[1], coord[0], coord[1])
+			}
+			if coordsToTotalDist[point] < dist {
+				area++
+			}
+		}
+	}
+
+	return area
+}
+
+func parseInputCoords(input string) [][2]int {
+	lines := strings.Split(input, "\n")
+	coords := [][2]int{} // [row, col]
+	for _, l := range lines {
+		c := strings.Split(l, ", ")
+		if len(c) == 2 {
+			coords = append(coords, [2]int{
+				util.StrToInt(c[0]),
+				util.StrToInt(c[1]),
+			})
+		}
+	}
+	return coords
+}
+
+func getBounds(coords [][2]int) (left int, right int, top int, bottom int) {
+	var (
+		boundLeft   = math.MaxInt16
+		boundRight  = -math.MaxInt16
+		boundTop    = math.MaxInt16
+		boundBottom = -math.MaxInt16
+	)
+	for _, c := range coords {
+		if c[0] < boundTop {
+			boundTop = c[0]
+		}
+		if c[0] > boundBottom {
+			boundBottom = c[0]
+		}
+		if c[1] < boundLeft {
+			boundLeft = c[1]
+		}
+		if c[1] > boundRight {
+			boundRight = c[1]
+		}
+	}
+	return boundLeft, boundRight, boundTop, boundBottom
+}