Snippet

project_euler/18.rb

Code:

# Project Euler Problem 18: Maximum Path Sum I

# https://projecteuler.net/problem=18

require_relative './helpers.rb'

def find(triangle, row)
    triangle[row].map!.with_index do |n, i|
        l = triangle[row + 1][i]
        r = triangle[row + 1][i + 1]
        l > r ? n.to_i + l.to_i : n.to_i + r.to_i
    end
    return triangle if row == 0
    return find(triangle, row - 1)
end

def solve(triangle)
    sum, path = find(triangle, triangle.size - 2)[0]
    return sum
end

example = [['3'], ['7', '4'], ['2', '4', '6'], ['8', '5', '9', '3']]
triangle = get_dataset(problem: 18).map { |line| line.split(' ') }

puts solve(example)
puts solve(triangle)

Output:

23
1074