C++ Tutorial/Function/function recursion — различия между версиями
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Текущая версия на 10:29, 25 мая 2010
Содержание
Demonstrate recursion
#include <iostream>
using namespace std;
int f(int n);
int main()
{
// use recursive version
cout << "4 factorial is " << f(4);
return 0;
}
int f(int n)
{
int answer;
if(n==1)
return(1);
answer = f(n-1)*n;
return(answer);
}4 factorial is 24
Print a string backwards using recursion
#include <iostream>
using namespace std;
void f(char *s);
int main()
{
char str[] = "this is a test";
f(str);
return 0;
}
void f(char *s)
{
if(*s)
f(s+1);
else
return;
cout << *s;
}tset a si siht
Recursive factorial function
#include <iostream>
using std::cout;
using std::endl;
#include <iomanip>
using std::setw;
unsigned long factorial( unsigned long ); // function prototype
int main()
{
for ( int counter = 0; counter <= 50; counter++ )
cout << setw( 2 ) << counter << "! = " << factorial( counter ) << endl;
return 0;
}
unsigned long factorial( unsigned long number )
{
if ( number <= 1 )
return 1;
else
return number * factorial( number - 1 );
}0! = 1 1! = 1 2! = 2 3! = 6 4! = 24 5! = 120 6! = 720 7! = 5040 8! = 40320 9! = 362880 10! = 3628800 11! = 39916800 12! = 479001600 13! = 1932053504 14! = 1278945280 15! = 2004310016 16! = 2004189184 17! = 4006445056 18! = 3396534272 19! = 109641728 20! = 2192834560 21! = 3099852800 22! = 3772252160 23! = 862453760 24! = 3519021056 25! = 2076180480 26! = 2441084928 27! = 1484783616 28! = 2919235584 29! = 3053453312 30! = 1409286144 31! = 738197504 32! = 2147483648 33! = 2147483648 34! = 0 35! = 0 36! = 0 37! = 0 38! = 0 39! = 0 40! = 0 41! = 0 42! = 0 43! = 0 44! = 0 45! = 0 46! = 0 47! = 0 48! = 0 49! = 0 50! = 0
The iterative factorial method.
#include <iostream>
using std::cout;
using std::endl;
#include <iomanip>
using std::setw;
unsigned long factorial( unsigned long );
int main()
{
for ( int counter = 0; counter <= 20; counter++ )
cout << setw( 2 ) << counter << "! = " << factorial( counter ) << endl;
return 0;
}
unsigned long factorial( unsigned long number )
{
unsigned long result = 1;
for ( unsigned long i = number; i >= 1; i-- )
result *= i;
return result;
}0! = 1 1! = 1 2! = 2 3! = 6 4! = 24 5! = 120 6! = 720 7! = 5040 8! = 40320 9! = 362880 10! = 3628800 11! = 39916800 12! = 479001600 13! = 1932053504 14! = 1278945280 15! = 2004310016 16! = 2004189184 17! = 4006445056 18! = 3396534272 19! = 109641728 20! = 2192834560
The recursive fibonacci function.
#include <iostream>
using std::cout;
using std::cin;
using std::endl;
unsigned long fibonacci( unsigned long );
int main()
{
cout << "fibonacci( 20 ) = " << fibonacci( 20 ) << endl;
cout << "fibonacci( 30 ) = " << fibonacci( 30 ) << endl;
cout << "fibonacci( 35 ) = " << fibonacci( 35 ) << endl;
return 0;
}
unsigned long fibonacci( unsigned long number )
{
if ( ( number == 0 ) || ( number == 1 ) )
return number;
else
return fibonacci( number - 1 ) + fibonacci( number - 2 );
}fibonacci( 20 ) = 6765 fibonacci( 30 ) = 832040 fibonacci( 35 ) = 9227465
