Solution for Advent of Code 2015 - Day 2: I Was Told There Would Be No Math

Link to the puzzle text

Part 1

For each paket, we need to find the surface area of the box. After parsing the input into the three integers for width w, height h and length l, the surface area for a box is 2 * (w * h + w * l + l * h). For the puzzle we also need add the smallest side of box again. We do this by adding min(w * h, w * l, l * h).

 

def wrapping_area(dimensions_line):
    l, w, h = dimensions_line.split("x")
    l = int(l)
    w = int(w)
    h = int(h)

    area = 2 * l * w + 2 * w * h + 2 * l * h + min(l * w, w * h, l * h)
    return area

This function passed the tests against the supplied inputs and for my real puzzle, we just loop over all lines in the input.

Part 2

In part 2 we need to calculate the length of a ribbon for the package. The length is made of two parts: the perimeter of the smallest side and a bow. The perimeter of the smallest side is 2 * (smallest dimension * second smallest dimension) or since we have only three dimensions: 2 * (sum of all dimension - largest dimension). The bow is simply the volume of the package length * width * height.

 

def ribbon_length(dimensions_line):
    l, w, h = dimensions_line.split("x")
    l = int(l)
    w = int(w)
    h = int(h)

    ribbon = 2 * (l + w + h - max(l, w, h))
    ribbon += l * w * h
    return ribbon

This was again tested against the supplied inputs and calcaluted in a loop for the real puzzle.

Link to my solutions