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Update double_factorial.cpp

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DarkWarrior703 2020-04-25 22:34:44 +03:00 committed by GitHub
parent e6874e4d18
commit 9fef832f57
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1 changed files with 6 additions and 7 deletions
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math/double_factorial.cpp
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@ -8,23 +8,22 @@ that have the same parity (odd or even) as n.
It is also called as semifactorial
of a number and is denoted by !! */
unsigned long long double_factorial_iterative(unsigned int n){
uint64_t double_factorial_iterative(unsigned int n){
unsigned long long res = 1;
for( unsigned long long i = n; i >= 0; i -= 2 ){
if(i == 0 || i == 1) return res;
for ( unsigned long long i = n; i >= 0; i -= 2 ) {
if (i == 0 || i == 1) return res;
res *= i;
}
}
/* Recursion can be costly for large numbers */
unsigned long long double_factorial_recursive(unsigned int n){
if(n <= 1) return 1;
uint64_t double_factorial_recursive(unsigned int n){
if (n <= 1) return 1;
return n * double_factorial_recursive(n - 2);
}
int main()
{
int main() {
int n{};
std::cin >> n;
assert(n >= 0);