130 lines
2.1 KiB
Go
130 lines
2.1 KiB
Go
package main
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import (
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aoc "AoC/2021/common"
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"bufio"
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"regexp"
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"strconv"
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)
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type line struct {
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x1, y1, x2, y2 int
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}
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func min(a, b int) int {
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if a < b {
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return a
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}
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return b
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}
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func max(a, b int) int {
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if a > b {
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return a
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}
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return b
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}
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func findIntersection(diagonal bool) func (*bufio.Scanner) int {
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return func (input *bufio.Scanner) int {
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var lines []line
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var xmax, ymax int
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re := regexp.MustCompile("[0-9]+")
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for input.Scan() {
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text := input.Text()
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numbers := re.FindAllString(text, -1)
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if len(numbers) != 4 {
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panic("Did not find 4 numbers")
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}
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var coords [4]int
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for i, n := range numbers {
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c, err := strconv.Atoi(n)
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if err != nil {
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panic(err)
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}
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coords[i] = c
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}
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xmax = max(xmax, max(coords[0], coords[2]))
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ymax = max(ymax, max(coords[1], coords[3]))
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// Only consider horizontal and vertical line if diagonal is false
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if diagonal || coords[0] == coords[2] || coords[1] == coords[3] {
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lines = append(lines, line{coords[0], coords[1], coords[2], coords[3]})
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}
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}
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diagram := make([][]int, ymax+1)
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for y := 0; y <= ymax; y++ {
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diagram[y] = make([]int, xmax+1)
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}
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for _, a := range lines {
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// Vertical line
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if a.x1 == a.x2 {
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for y := min(a.y1, a.y2); y <= max(a.y1, a.y2); y++ {
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diagram[y][a.x1]++
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}
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continue
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}
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// Horizontal line
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if a.y1 == a.y2 {
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for x := min(a.x1, a.x2); x <= max(a.x1, a.x2); x++ {
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diagram[a.y1][x]++
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}
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continue
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}
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// Otherwise we have a diagonal line
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length := max(a.x1, a.x2) - min(a.x1, a.x2) + 1
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for i := 0; i < length; i++ {
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x := a.x1 + i
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if (a.x1 > a.x2) {
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x = a.x1 - i
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}
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y := a.y1 + i
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if (a.y1 > a.y2) {
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y = a.y1 - i
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}
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diagram[y][x]++
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}
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}
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points := 0
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for y := 0; y <= ymax; y++ {
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for x := 0; x <= xmax; x++ {
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if diagram[y][x] > 1 {
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points++
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}
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}
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}
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return points
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}
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}
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func main() {
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aoc := aoc.New(2021, 5)
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aoc.Test(`0,9 -> 5,9
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8,0 -> 0,8
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9,4 -> 3,4
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2,2 -> 2,1
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7,0 -> 7,4
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6,4 -> 2,0
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0,9 -> 2,9
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3,4 -> 1,4
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0,0 -> 8,8
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5,5 -> 8,2`, []int{5, 12})
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aoc.Solution(1, findIntersection(false))
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aoc.Solution(2, findIntersection(true))
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}
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