Day14

2024/gareth/day14/day14.go

@@ -0,0 +1,172 @@
+package day14
+
+import (
+	"fmt"
+	"strconv"
+	"strings"
+)
+
+type Robot struct {
+	px, py int // position
+	vx, vy int // velocity
+}
+
+func Part1(input string) int {
+	// Parse the input
+	lines := strings.Split(input, "\n")
+	var robots []Robot
+	for _, line := range lines {
+		robot := ParseRobot(line)
+		robots = append(robots, robot)
+	}
+
+	// Define grid size
+	gridWidth := 101
+	gridHeight := 103
+
+	// Update robot positions for 100 seconds
+	for i := 0; i < 100; i++ {
+		for j := range robots {
+			robots[j].UpdatePosition(gridWidth, gridHeight)
+		}
+	}
+
+	// Count the robots in each quadrant
+	q1, q2, q3, q4 := CountRobotsInQuadrants(robots, gridWidth, gridHeight)
+	fmt.Printf("Quadrant counts: Q1=%d, Q2=%d, Q3=%d, Q4=%d\n", q1, q2, q3, q4)
+
+	// Calculate the safety factor
+	safetyFactor := CalculateSafetyFactor(q1, q2, q3, q4)
+	fmt.Printf("Safety Factor: %d\n", safetyFactor)
+	return safetyFactor
+}
+
+func Part2(input string) int {
+	// Parse the input
+	lines := strings.Split(input, "\n")
+	var robots []Robot
+	for _, line := range lines {
+		robot := ParseRobot(line)
+		robots = append(robots, robot)
+	}
+
+	// Define grid size
+	gridWidth := 101
+	gridHeight := 103
+
+	// Update robot positions for 100 seconds
+	for i := 0; i < 6285; i++ {
+		for j := range robots {
+			robots[j].UpdatePosition(gridWidth, gridHeight)
+		}
+	}
+
+	DisplayGrid(robots, gridWidth, gridHeight)
+	return 2
+}
+
+// ParseRobot takes a line of input and converts it to a Robot struct
+func ParseRobot(line string) Robot {
+	parts := strings.Split(line, " ")
+	posParts := strings.Split(parts[0][2:], ",") // Extract p=x,y and split
+	velParts := strings.Split(parts[1][2:], ",") // Extract v=x,y and split
+
+	px, _ := strconv.Atoi(posParts[0])
+	py, _ := strconv.Atoi(posParts[1])
+	vx, _ := strconv.Atoi(velParts[0])
+	vy, _ := strconv.Atoi(velParts[1])
+
+	return Robot{px, py, vx, vy}
+}
+
+// UpdatePosition updates the position of a robot, considering the wrap-around
+func (r *Robot) UpdatePosition(gridWidth, gridHeight int) {
+	r.px = (r.px + r.vx + gridWidth) % gridWidth
+	r.py = (r.py + r.vy + gridHeight) % gridHeight
+}
+
+// CountRobotsInQuadrants counts the number of robots in each of the four quadrants
+func CountRobotsInQuadrants(robots []Robot, width, height int) (int, int, int, int) {
+	midX := width / 2
+	midY := height / 2
+
+	q1, q2, q3, q4 := 0, 0, 0, 0
+
+	for _, r := range robots {
+		if r.px == midX || r.py == midY {
+			// Skip robots on the middle line
+			continue
+		}
+		if r.px < midX && r.py < midY {
+			q1++ // Top-left quadrant
+		} else if r.px > midX && r.py < midY {
+			q2++ // Top-right quadrant
+		} else if r.px < midX && r.py > midY {
+			q3++ // Bottom-left quadrant
+		} else if r.px > midX && r.py > midY {
+			q4++ // Bottom-right quadrant
+		}
+	}
+
+	return q1, q2, q3, q4
+}
+
+// CalculateSafetyFactor multiplies the number of robots in each quadrant
+func CalculateSafetyFactor(q1, q2, q3, q4 int) int {
+	return q1 * q2 * q3 * q4
+}
+
+// DisplayGrid displays the current state of the grid
+func DisplayGrid(robots []Robot, width, height int) {
+	grid := make([][]rune, height)
+	for i := range grid {
+		grid[i] = make([]rune, width)
+		for j := range grid[i] {
+			grid[i][j] = '.'
+		}
+	}
+	for _, r := range robots {
+		grid[r.py][r.px] = '#'
+	}
+	for _, row := range grid {
+		fmt.Println(string(row))
+	}
+}
+
+// FindEasterEgg determines the fewest number of seconds that must elapse for the robots to display the Easter egg
+func FindEasterEgg(robots []Robot, width, height int) int {
+	smallestArea := width * height
+	bestTime := 0
+	for t := 6285; t < 6286; t++ { // Large upper limit to search
+		// Update robot positions
+		for i := range robots {
+			robots[i].UpdatePosition(width, height)
+		}
+		// Calculate the bounding box of all robot positions
+		minX, minY := width, height
+		maxX, maxY := 0, 0
+		for _, r := range robots {
+			if r.px < minX {
+				minX = r.px
+			}
+			if r.px > maxX {
+				maxX = r.px
+			}
+			if r.py < minY {
+				minY = r.py
+			}
+			if r.py > maxY {
+				maxY = r.py
+			}
+		}
+
+		area := (maxX - minX + 1) * (maxY - minY + 1)
+		if area < smallestArea {
+			smallestArea = area
+			bestTime = t + 1
+			fmt.Printf("Time: %d\n", bestTime)
+			DisplayGrid(robots, width, height)
+		}
+	}
+	return bestTime
+}