Advent of Code 2015 Day 21

Author

Nathan Moore

— Day 21: RPG Simulator 20XX —

Buy things from the shop to defeat the boss.

You have 100 hit points. The boss’s actual stats are in your puzzle input. What is the least amount of gold you can spend and still win the fight?

with open('data-2015-21.txt', 'r') as f:
    inp = f.read().splitlines()

inp_dict = {x.split(':')[0]: int(x.split(':')[1]) for x in inp}

b_hp = inp_dict['Hit Points']
b_d = inp_dict['Damage']
b_a = inp_dict['Armor']

# me
m_hp = 100

How long can we survive with different damage and armor variables?

def battle(dam, def_):
    # how many turns I can survive for
    m_turns = m_hp / max(b_d - def_, 1)
    # how many turns the boss can survive for
    b_turns = b_hp / max(dam - b_a, 1)
    # if I can survive longer than the boss, then I win
    return m_turns > b_turns

Lists of damage and armor possibilities

# Weapons:    Cost  Damage  Armor
# Dagger        8     4       0
# Shortsword   10     5       0
# Warhammer    25     6       0
# Longsword    40     7       0
# Greataxe     74     8       0
# 
# Armor:      Cost  Damage  Armor
# Leather      13     0       1
# Chainmail    31     0       2
# Splintmail   53     0       3
# Bandedmail   75     0       4
# Platemail   102     0       5
# 
# Rings:      Cost  Damage  Armor
# Damage +1    25     1       0
# Damage +2    50     2       0
# Damage +3   100     3       0
# Defense +1   20     0       1
# Defense +2   40     0       2
# Defense +3   80     0       3

weapons_cost = [8, 10, 25, 40, 74]
weapons_damage = [4, 5, 6, 7, 8]
rings_cost_d = [0, 25, 50, 100]
rings_damage = [0, 1, 2, 3]

armor_cost = [0, 13, 31, 53, 75, 102]
armor_defense = [0, 1, 2, 3, 4, 5]
rings_cost_a = [0, 20, 40, 80]
rings_defense = [0, 1, 2, 3]

It looks like I want to use product to create a dataframe

import pandas as pd
import itertools

result = pd.DataFrame(list(itertools.product(weapons_damage, 
                                             rings_damage, 
                                             armor_defense, 
                                             rings_defense))
                     ).rename(columns={0:'w_dam', 1:'r_dam', 2:'a_def', 3:'r_def'})

result['dam'] = result['w_dam'] + result['r_dam']
result['def'] = result['a_def'] + result['r_def']

wpc = pd.DataFrame([weapons_cost, weapons_damage], index=['wpc', 'w_dam']).T
rcd = pd.DataFrame([rings_cost_d, rings_damage], index=['rcd', 'r_dam']).T
arc = pd.DataFrame([armor_cost, armor_defense], index=['arc', 'a_def']).T
rca = pd.DataFrame([rings_cost_a, rings_defense], index=['rca', 'r_def']).T

result = pd.merge(result, wpc, on='w_dam')
result = pd.merge(result, rcd, on='r_dam')
result = pd.merge(result, arc, on='a_def')
result = pd.merge(result, rca, on='r_def')

result['cost'] = result['wpc'] + result['rcd'] + result['arc'] + result['rca']

result['win'] = result.apply(lambda row: battle(row['dam'], row['def']), axis=1)

result[result['win']==True].nsmallest(1, 'cost')

# 111

	w_dam	r_dam	a_def	r_def	dam	def	wpc	rcd	arc	rca	cost	win
298	7	0	2	2	7	4	40	0	31	40	111	True

— Part Two —

What is the most amount of gold you can spend and still lose the fight?

result[result['win']==False].nlargest(1, 'cost')

# 188

	w_dam	r_dam	a_def	r_def	dam	def	wpc	rcd	arc	rca	cost	win
75	4	3	0	3	7	3	8	100	0	80	188	False