aoc2023/day-9/one.go

package main

// next returns the next value in the sequence
func next(nums []int) int {
	diffs := []int{}
	for i := 1; i < len(nums); i++ {
		diffs = append(diffs, nums[i]-nums[i-1])
	}

	if allEqual(diffs) {
		return nums[len(nums)-1] + diffs[len(diffs)-1]
	}
	return nums[len(nums)-1] + next(diffs)
}

// one returns the sum of all next values
func one(lines []string) int {
	sum := 0
	for _, line := range lines {
		nums := convertToInts(line)
		sum += next(nums)
	}

	return sum
}