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Interview Question for Software Engineer at Google:
May 24, 2010
Write a function in C/C++ that returns the number of zeros contained in the factorial of the number that is passed to it.
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Answers & Comments (5)
Jun 5, 2010
works for 20 but not for 30...
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0 of 2 people found this helpful
Jun 20, 2010
The answer is simply:
int func(int number_to_get_factorial_of) {
return 0;
}
int func(int number_to_get_factorial_of) {
return 0;
}
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Jun 20, 2010
Assuming "int" can hold the whole factorial:
int func(int x) {
int factorial = 1;
int zeros = 0;
while (x) {
factorial *= x--;
}
while (factorial) {
zeros += (factorial % 10 == 0);
factorial /= 10;
}
return zeros;
}
int func(int x) {
int factorial = 1;
int zeros = 0;
while (x) {
factorial *= x--;
}
while (factorial) {
zeros += (factorial % 10 == 0);
factorial /= 10;
}
return zeros;
}
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1 of 1 people found this helpful
Jan 1, 2011
The previous poster is correct, but would fail for large numbers.
George is right that you just need the number of 5's in the prime factorization (there will always be lots of 2's), but dividing n by 5 does not quite give that to you.
You need n/5 + n/25 + n/125 + ..... In time the terms become 0 and you can stop.
George is right that you just need the number of 5's in the prime factorization (there will always be lots of 2's), but dividing n by 5 does not quite give that to you.
You need n/5 + n/25 + n/125 + ..... In time the terms become 0 and you can stop.
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1 of 3 people found this helpful
by George:
def number_of_zeros( n ):
return n / 5