2 решения

Задание:
Given is array containing N numbers, A[0], A[1], ... A[N-1]. Compute the array B of length N, such that B[i] = A[0]*A[1]*...A[i-1]*A[i+1]...*A[N-1]. Algorithm should work in time O(N), memory O(1) and can't use division.

Решение 1:
Конечно тут не чисто O(N), так как за логарифмом и экспонентой вряд ли O(1).

	from math import log, exp
	def solve(a):
	p = reduce(lambda x, y: x*y, a)
	return [int(round( p * exp(-log(x)) )) for x in a]

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Решение 2:
А тут чистенько все вроде.

	def solve(a):
	temp = 1
	b = []
	for x in a:
	temp *= x
	b.append(temp)
	prev = 1
	for i in xrange(len(a) - 2, -1, -1):
	b[i + 1] = prev * b[i]
	prev *= a[i + 1]
	b[0] = prev
	return b

view raw gistfile1.py hosted with ❤ by GitHub

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