A recursive
function is a function which either calls itself or is in a potential cycle of
function calls. Here some simple examples of recursive functions are given like
factorial of a number, Fibonacci number series, combination, permutation &
tower of Hanoi.
Source code:
#include <stdio.h>
#include <conio.h>
// n! = n*(n-1)! & 0! = 1
double fact(unsigned int number)
{
if (number ==
0)
return(1.00);
else
return(number*fact(number -
1));
}
//fib(n) = fib(n-1)+fib(n-2) for n>2
& fib(0) =0 ,fib(1) =1;
unsigned int fib_num(unsigned int number)
{
if (number>=2)
return(fib_num(number - 1)
+ fib_num(number - 2));
else
{
if (number)
return(1);
else
return(0);
}
}
//nCr = (n-1)C(r-1)+(n-1)C(r-1) if
r<=n else 0; & nC0=1;
unsigned int nCr(unsigned int _tot,unsigned int _comb)
{
if (!_comb)
{
return 1;
}
else if (_comb <= _tot)
{
return (nCr(_tot -
1, _comb - 1) + nCr(_tot -
1, _comb));
}
else
{
return 0;
}
}
//nPr = (n-r+1)*nP(r-1) if r<=n else
0; & nP0=1;
int nPr(unsigned int _tot, unsigned int _perm)
{
if (!_perm)
{
return 1;
}
else if (_perm <= _tot)
{
(_tot - _perm + 1)
* nPr(_tot, _perm -
1);
}
else
{
return 0;
}
return(fact(_perm)*nCr(_tot, _perm));
}
// Solve for first (n-1) disks, then
for (n-2),(n-3)...
void tower_of_hanoi(unsigned int number, char *B, char *A, char *E)
{
if (number)
{
tower_of_hanoi(number -
1, B, E, A);
printf("move disks from tower%s to tower%s", B, E);
printf("\n");
tower_of_hanoi(number -
1, A, B, E);
}
return;
}
int main()
{
printf("**Recursive
Function Examples**\n");
printf("\n_______________________________________________________________\n");
printf("Factorial
of 7 = %f\n", fact(7));
printf("\n_______________________________________________________________\n");
printf("Fibonacci
numbers series up 12 numbers\n");
for (size_t i =
0; i < 12; i++)
{
printf(" %d", fib_num(i));
}
printf("\n_______________________________________________________________\n");
printf("\n**combination
& permutation**");
printf("\n
23 C 3 = %d", nCr(23, 3));
printf("\n
23 P 3 = %d", nPr(23, 3));
printf("\n_______________________________________________________________\n");
printf("\nSolution
of tower of hanoi for 4 disks\n");
tower_of_hanoi(4, "1", "2", "3");
printf("\n_______________________________________________________________\n");
getchar();
return 0;
}
Output:
