aoc2023/day-14/one.go

package main

// getload returns the load of all boulders for a single image
func getload(raw []string) int {
	load := 0
	for _, line := range raw {
		for i, r := range line {
			if r == 'O' {
				load += (i + 1)
			}
		}
	}

	return load
}

// spacesToRight determines the number of spaces right of a boulder
func spacesToRight(i int, line string) int {
	num := 0
outer:
	for i += 1; i < len(line); i++ {
		switch line[i] {
		case '.':
			num++
		case '#', 'O':
			break outer
		}
	}
	return num
}

// rollRight rolls a boulder right until there's no space
func rollRight(line string) string {
	for i := len(line) - 1; i >= 0; i-- {
		if line[i] == 'O' {
			n := spacesToRight(i, line)
			if n == 0 {
				continue
			}
			line = replaceAtIndex(line, '.', i)
			line = replaceAtIndex(line, 'O', i+n)
		}
	}

	return line
}

// one returns the load of all boulders after a single image transposition+roll
func one(lines []string) int {
	image := newImg(len(lines))
	copy(image.raw, lines)

	for i, line := range image.transposed() {
		image.raw[i] = rollRight(line)
	}

	return getload(image.raw)
}