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Find the seed of a number.
Eg : 1716 = 143*1*4*3 =1716 so 143 is the seed of 1716. find all possible seed for a given number.
辗转相除法，由性质可利用 sqrt(num) <= seed_number <= num/2 缩小范围。
def seed_number(num) seed = Math.sqrt(num).to_i while seed <= num / 2 if num % seed == 0 product = temp = seed while temp != 0 product *= temp%10 temp /= 10 end return seed if product == num end seed += 1 end end
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原文地址：http://www.cnblogs.com/lilixu/p/4575028.html
