aoc2023/day11/day11.go

package day11

import (
	"gitea.paas.celticinfo.fr/oabrivard/aoc2023/utils"
)

type Coord struct {
	row int
	col int
}

func expandUniverse(lines []string) [][]byte {
	height := len(lines)
	width := len(lines[0])
	isRowEmpty := make([]bool, height)
	isColEmpty := make([]bool, width)
	emptyColCount := 0
	emptyRowCount := 0

	for row, l := range lines {
		isRowEmpty[row] = true
		emptyRowCount++
		for _, c := range l {
			if c == '#' {
				isRowEmpty[row] = false
				emptyRowCount--
				break
			}
		}
	}

	for col := 0; col < width; col++ {
		isColEmpty[col] = true
		emptyColCount++
		for row := 0; row < height; row++ {
			if lines[row][col] == '#' {
				isColEmpty[col] = false
				emptyColCount--
				break
			}
		}
	}

	result := make([][]byte, height+emptyRowCount)
	destRow := 0

	for row, l := range lines {
		destCol := 0
		result[destRow] = make([]byte, width+emptyColCount)
		if isRowEmpty[row] {
			result[destRow+1] = make([]byte, width+emptyColCount)
			for destCol := range result[destRow] {
				result[destRow][destCol] = '.'
				result[destRow+1][destCol] = '.'
			}
			destRow += 2
		} else {
			for col := range l {
				result[destRow][destCol] = lines[row][col]
				destCol++
				if isColEmpty[col] {
					result[destRow][destCol] = lines[row][col]
					destCol++
				}
			}
			destRow++
		}
	}

	return result
}

func getUniverseAsInt(universe [][]byte) ([][]int, []Coord) {
	height := len(universe)
	width := len(universe[0])
	result := make([][]int, height)
	coords := []Coord{}
	galaxyID := 0

	for row, line := range universe {
		result[row] = make([]int, width)

		for col, c := range line {
			if c == '#' {
				result[row][col] = galaxyID
				coords = append(coords, Coord{row, col})
				galaxyID++
			} else {
				result[row][col] = -1
			}
		}
	}

	return result, coords
}

func SumLengths(lines []string) int {
	result := 0
	_, coords := getUniverseAsInt(expandUniverse(lines))
	galaxyCount := len(coords) - 1

	for i := 0; i < galaxyCount; i++ {
		for j := i + 1; j <= galaxyCount; j++ {
			r1_c1 := coords[i]
			r2_c2 := coords[j]
			dist := 0
			//dist2 := float64(0)
			ab := r2_c2.row - r1_c1.row
			if ab == 0 {
				dist = utils.AbsInt(r2_c2.col - r1_c1.col)
			} else {
				bc := r2_c2.col - r1_c1.col
				if bc == 0 {
					dist = utils.AbsInt(r2_c2.row - r1_c1.row)
				} else {
					//dist2 = math.Sqrt(float64(utils.IntPow(ab, 2) + utils.IntPow(bc, 2)))        // euclidian distance
					dist = utils.AbsInt(r2_c2.row-r1_c1.row) + utils.AbsInt(r2_c2.col-r1_c1.col) // Manhattan distance
				}
			}
			result += dist
			//fmt.Printf("(%d,%d) = %d, %v\n", i, j, dist, dist2)
		}
	}

	return result
}

func getEmptyLines(lines []string) ([]bool, []bool) {
	height := len(lines)
	width := len(lines[0])
	isRowEmpty := make([]bool, height)
	isColEmpty := make([]bool, width)
	emptyColCount := 0
	emptyRowCount := 0

	for row, l := range lines {
		isRowEmpty[row] = true
		emptyRowCount++
		for _, c := range l {
			if c == '#' {
				isRowEmpty[row] = false
				emptyRowCount--
				break
			}
		}
	}

	for col := 0; col < width; col++ {
		isColEmpty[col] = true
		emptyColCount++
		for row := 0; row < height; row++ {
			if lines[row][col] == '#' {
				isColEmpty[col] = false
				emptyColCount--
				break
			}
		}
	}

	return isRowEmpty, isColEmpty
}

func getCoords(universe []string, expansion int) []Coord {
	coords := []Coord{}
	galaxyID := 0
	deltaRow := 0

	isRowEmpty, isColEmpty := getEmptyLines(universe)

	for row, line := range universe {
		deltaCol := 0

		if isRowEmpty[row] {
			deltaRow += expansion
		} else {
			for col, c := range line {
				if isColEmpty[col] {
					deltaCol += expansion
				} else {
					if c == '#' {
						coords = append(coords, Coord{row + deltaRow, col + deltaCol})
						galaxyID++
					}
				}
			}
		}
	}

	return coords
}

func SumLengths2(lines []string, expansion int) int {
	result := 0

	coords := getCoords(lines, expansion)
	galaxyCount := len(coords) - 1

	for i := 0; i < galaxyCount; i++ {
		for j := i + 1; j <= galaxyCount; j++ {
			r1_c1 := coords[i]
			r2_c2 := coords[j]
			dist := 0
			ab := r2_c2.row - r1_c1.row
			if ab == 0 {
				dist = utils.AbsInt(r2_c2.col - r1_c1.col)
			} else {
				bc := r2_c2.col - r1_c1.col
				if bc == 0 {
					dist = utils.AbsInt(r2_c2.row - r1_c1.row)
				} else {
					//dist2 = math.Sqrt(float64(utils.IntPow(ab, 2) + utils.IntPow(bc, 2)))        // euclidian distance
					dist = utils.AbsInt(r2_c2.row-r1_c1.row) + utils.AbsInt(r2_c2.col-r1_c1.col) // Manhattan distance
				}
			}
			result += dist
			//fmt.Printf("(%d,%d) = %d, %v\n", i, j, dist, dist2)
		}
	}

	return result
}