Solution to problem 2 in Python

src/Year_2015/P2.py

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+# --- Day 2: I Was Told There Would Be No Math ---
+
+# The elves are running low on wrapping paper, and so they need to submit an
+# order for more. They have a list of the dimensions (length l, width w, and
+# height h) of each present, and only want to order exactly as much as they
+# need.
+
+# Fortunately, every present is a box (a perfect right rectangular prism),
+# which makes calculating the required wrapping paper for each gift a little
+# easier: find the surface area of the box, which is 2*l*w + 2*w*h + 2*h*l.
+# The elves also need a little extra paper for each present: the area of the
+# smallest side.
+
+# For example:
+
+#     A present with dimensions 2x3x4 requires 2*6 + 2*12 + 2*8 = 52 square
+# feet of wrapping paper plus 6 square feet of slack, for a total of 58 square
+# feet.
+#     A present with dimensions 1x1x10 requires 2*1 + 2*10 + 2*10 = 42 square
+# feet of wrapping paper plus 1 square foot of slack, for a total of 43 square
+# feet.
+
+# All numbers in the elves' list are in feet. How many total square feet of
+# wrapping paper should they order?
+
+from itertools import combinations
+from math import prod
+
+with open("files/P2.txt") as f:
+    boxes = [line for line in f.read().strip().split()]
+
+
+def part_1() -> None:
+    wrapping_paper = 0
+    for box in boxes:
+        sides = list(combinations(box.split("x"), 2))
+        extra = min(int(dims[0]) * int(dims[1]) for dims in sides)
+        box_area = sum(2 * int(dims[0]) * int(dims[1]) for dims in sides)
+        wrapping_paper += box_area + extra
+
+    print(f"They will need {wrapping_paper} sqf. of wrapping paper")
+
+
+# --- Part Two ---
+
+# The elves are also running low on ribbon. Ribbon is all the same width, so
+# they only have to worry about the length they need to order, which they would
+# again like to be exact.
+
+# The ribbon required to wrap a present is the shortest distance around its
+# sides, or the smallest perimeter of any one face. Each present also requires
+# a bow made out of ribbon as well; the feet of ribbon required for the perfect
+# bow is equal to the cubic feet of volume of the present. Don't ask how they
+# tie the bow, though; they'll never tell.
+
+# For example:
+
+#     A present with dimensions 2x3x4 requires 2+2+3+3 = 10 feet of ribbon to
+# wrap the present plus 2*3*4 = 24 feet of ribbon for the bow, for a total of
+# 34 feet.
+#     A present with dimensions 1x1x10 requires 1+1+1+1 = 4 feet of ribbon to
+# wrap the present plus 1*1*10 = 10 feet of ribbon for the bow, for a total of
+# 14 feet.
+
+# How many total feet of ribbon should they order?
+
+
+def part_2() -> None:
+    ribbon = 0
+    for box in boxes:
+        sides = list(map(int, box.split("x")))
+        bow = prod(sides)
+        sides.remove(max(sides))
+        wrapping = 2 * sides[0] + 2 * sides[1]
+        ribbon += wrapping + bow
+    print(f"They will need {ribbon} sqf. of ribbon")
+
+
+if __name__ == "__main__":
+    part_1()
+    part_2()