""" Problem 31: https://projecteuler.net/problem=31 Coin sums In England the currency is made up of pound, £, and pence, p, and there are eight coins in general circulation: 1p, 2p, 5p, 10p, 20p, 50p, £1 (100p) and £2 (200p). It is possible to make £2 in the following way: 1×£1 + 1×50p + 2×20p + 1×5p + 1×2p + 3×1p How many different ways can £2 be made using any number of coins? Hint: > There are 100 pence in a pound (£1 = 100p) > There are coins(in pence) are available: 1, 2, 5, 10, 20, 50, 100 and 200. > how many different ways you can combine these values to create 200 pence. Example: to make 6p there are 5 ways 1,1,1,1,1,1 1,1,1,1,2 1,1,2,2 2,2,2 1,5 to make 5p there are 4 ways 1,1,1,1,1 1,1,1,2 1,2,2 5 """ def solution(pence: int = 200) -> int: """Returns the number of different ways to make X pence using any number of coins. The solution is based on dynamic programming paradigm in a bottom-up fashion. >>> solution(500) 6295434 >>> solution(200) 73682 >>> solution(50) 451 >>> solution(10) 11 """ coins = [1, 2, 5, 10, 20, 50, 100, 200] number_of_ways = [0] * (pence + 1) number_of_ways[0] = 1 # base case: 1 way to make 0 pence for coin in coins: for i in range(coin, pence + 1, 1): number_of_ways[i] += number_of_ways[i - coin] return number_of_ways[pence] if __name__ == "__main__": assert solution(200) == 73682