https://projecteuler.net/problem=8
毎回13個の数字を掛け算すればよいですが、もう少し頑張れば計算量を減らせます。0が13個の間に何個あるのかと最後の0のあと積を記憶しておけばよいです。
# e008.mojo import sys struct ProductGenerator: var L: Int var ds: DynamicVector[Int] var num_zeros: Int var product: Int var i: Int fn __init__(inout self, L: Int, ds: DynamicVector[Int], nz: Int, p: Int): self.L = L self.ds = ds self.num_zeros = nz self.product = p self.i = -1 fn next(inout self) -> Int: self.i += 1 if self.i != 0 and self.ds[self.i-1] == 0: self.num_zeros -= 1 elif self.i != 0 and self.num_zeros == 0: self.product /= self.ds[self.i-1] if self.ds[self.i+self.L-1] == 0: self.num_zeros += 1 self.product = 1 return 0 else: self.product *= self.ds[self.i+self.L-1] if self.num_zeros == 0: return self.product else: return 0 @staticmethod fn create(s: String, L: Int) raises -> ProductGenerator: var ds = DynamicVector[Int]() for i in range(len(s)): ds.push_back(atol(s[i])) var nz = 0 var p = 1 for i in range(L-1): if ds[i] == 0: nz += 0 p = 1 else: p *= ds[i] return ProductGenerator(L, ds, nz, p) fn f(str_digits: String, L: Int) raises -> Int: var pg = ProductGenerator.create(str_digits, L) var max_p = 0 for i in range(len(str_digits) - L + 1): let p = pg.next() if p > max_p: max_p = p return max_p fn main() raises: let str_digits = ( '73167176531330624919225119674426574742355349194934' + '96983520312774506326239578318016984801869478851843' + '85861560789112949495459501737958331952853208805511' + '12540698747158523863050715693290963295227443043557' + '66896648950445244523161731856403098711121722383113' + '62229893423380308135336276614282806444486645238749' + '30358907296290491560440772390713810515859307960866' + '70172427121883998797908792274921901699720888093776' + '65727333001053367881220235421809751254540594752243' + '52584907711670556013604839586446706324415722155397' + '53697817977846174064955149290862569321978468622482' + '83972241375657056057490261407972968652414535100474' + '82166370484403199890008895243450658541227588666881' + '16427171479924442928230863465674813919123162824586' + '17866458359124566529476545682848912883142607690042' + '24219022671055626321111109370544217506941658960408' + '07198403850962455444362981230987879927244284909188' + '84580156166097919133875499200524063689912560717606' + '05886116467109405077541002256983155200055935729725' + '71636269561882670428252483600823257530420752963450') let args = sys.argv() let L = atol(args[1]) print(f(String(str_digits), L))