2018 day 11 - summing subgrids of a 2D grid

2018/day11/main.go

@@ -0,0 +1,117 @@
+package main
+
+import (
+	"flag"
+	"fmt"
+	"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"))
+		fmt.Println("Output:", ans)
+	}
+}
+
+// 300x300 grid
+func part1(input string) string {
+	gridSN := parseInputs(input)
+
+	grid := generateGrid(gridSN)
+
+	// find best 3x3 grid
+	deltas := [][2]int{
+		{-1, -1},
+		{-1, 0},
+		{-1, 1},
+		{0, -1},
+		{0, 0},
+		{0, 1},
+		{1, -1},
+		{1, 0},
+		{1, 1},
+	}
+	var best int
+	var topLeftCorner [2]int
+	for x := 2; x < 300; x++ {
+		for y := 2; y < 300; y++ {
+			sum := 0
+			for _, d := range deltas {
+				sum += grid[x+d[0]][y+d[1]]
+			}
+			if sum > best {
+				best = sum
+				topLeftCorner = [2]int{x - 1, y - 1}
+			}
+		}
+	}
+
+	return fmt.Sprintf("%d,%d", topLeftCorner[0], topLeftCorner[1])
+}
+
+func part2(input string) string {
+	gridSN := parseInputs(input)
+
+	grid := generateGrid(gridSN)
+
+	var bestPower int
+	var xYSize [3]int
+
+	for x := 1; x <= 300; x++ {
+		for y := 1; y <= 300; y++ {
+			var sum int
+			for edge := 0; edge+x <= 300 && edge+y <= 300; edge++ {
+				sum += grid[x+edge][y+edge]
+				for add := 0; add < edge; add++ {
+					sum += grid[x+add][y+edge]
+					sum += grid[x+edge][y+add]
+				}
+				if sum > bestPower {
+					bestPower = sum
+					xYSize = [3]int{x, y, edge + 1}
+				}
+			}
+		}
+	}
+
+	return fmt.Sprintf("%d,%d,%d", xYSize[0], xYSize[1], xYSize[2])
+}
+
+func parseInputs(input string) int {
+	return util.StrToInt(strings.TrimSpace(input))
+}
+
+func generateGrid(gridSN int) [][]int {
+	oneIndexedGrid := make([][]int, 301) // X, Y
+
+	for i := 1; i <= 300; i++ {
+		oneIndexedGrid[i] = make([]int, 301)
+	}
+
+	for x := 1; x <= 300; x++ {
+		for y := 1; y <= 300; y++ {
+			rackID := x + 10
+			power := rackID * y
+			power += gridSN
+			power *= rackID
+			// keep hundreds
+			power /= 100
+			power %= 10
+
+			power -= 5
+			oneIndexedGrid[x][y] = power
+		}
+	}
+
+	return oneIndexedGrid
+}