aoc2023/day14/day14.go

package day14

import (
	"fmt"
	"strings"

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

func SumWeights(lines []string) int {
	height := len(lines)
	maxDistFromTop := make([]int, len(lines[0]))

	sum := 0

	for i, line := range lines {
		for j, b := range line {
			switch b {
			case '#':
				maxDistFromTop[j] = i + 1
			case 'O':
				// Move it top and add its weight at its new place to the sume
				sum += height - maxDistFromTop[j]

				// change max top to indicate the a rock has been inserted
				maxDistFromTop[j]++
			}
		}
	}

	return sum
}

func Move(board [][]byte, direction string) (int, string) {
	height := len(board)
	maxDistFromTop := make([]int, len(board[0]))

	sum := 0

	for i, line := range board {
		for j, b := range line {
			switch b {
			case '#':
				maxDistFromTop[j] = i + 1
			case 'O':
				// Move it top and add its weight at its new place to the sume
				board[i][j] = '.'
				board[maxDistFromTop[j]][j] = 'O'
				sum += height - maxDistFromTop[j]

				// change max top to indicate the a rock has been inserted
				maxDistFromTop[j]++
			}
		}
	}

	var id strings.Builder
	id.WriteString(direction)
	for _, line := range board {
		id.WriteString(string(line))
	}

	/*
		for _, line := range board {
			fmt.Println(string(line))
		}
		fmt.Println("")
	*/

	key := id.String()
	return sum, key
}

func SumWeightsAfterTilts(lines []string) int {
	results2 := []int{}
	results := []int{}
	board := [][]byte{}
	boardID := ""
	boardExists := map[string]bool{}

	for _, line := range lines {
		board = append(board, []byte(line))
	}

	for i := 0; i < 1000; i++ {
		count := 0

		_, boardID = Move(board, "NORTH")

		if boardExists[boardID] {
			count++
		} else {
			boardExists[boardID] = true
		}

		board = utils.RotateClockwise[byte](board)

		_, boardID = Move(board, "WEST")

		if boardExists[boardID] {
			count++
		} else {
			boardExists[boardID] = true
		}

		board = utils.RotateClockwise[byte](board)

		_, boardID = Move(board, "SOUTH")

		if boardExists[boardID] {
			count++
		} else {
			boardExists[boardID] = true
		}

		board = utils.RotateClockwise[byte](board)

		_, boardID = Move(board, "EAST")

		if boardExists[boardID] {
			count++
		} else {
			boardExists[boardID] = true
		}

		board = utils.RotateClockwise[byte](board)

		if count == 4 {
			result := 0

			for k, line := range board {
				for _, b := range line {
					if b == 'O' {
						result += len(lines) - k
					}
				}
			}
			results = append(results, result)
			results2 = append(results2, i)
		}

	}

	end := 1
	for ; end < len(results)-1; end++ {
		if results[end] == results[0] && results[end+1] == results[1] {
			break
		}
	}

	idx := ((1_000_000_000 - results2[0]) % end) - 1
	fmt.Println(results[idx])

	return results[idx]
}