Page 170 - DCAP407_DATA_STRUCTURE

Unit 9: Recursion

By definition, 1 is the value for 0!. Let us compute the factorial of 5. Figure 9.2 depicts the factorial of 5.

Figure 9.2: Factorial of 5

But computations will be done in reverse order as depicted in figure 9.3.

Figure 9.3: Computations for Factorial of 5 in
Reverse Order

0! = 1
1! = 1 * 0! = 1 * 1 =1
2! = 2 * 1! = 2 * 1 = 2
3! = 3 * 2! = 3 * 2 =6

4! = 4 * 3! = 4 * 6 = 24
5! = 5 * 4! = 5 * 24 = 120

Program that computes the factorial of a number using recursion.

#include<stdio.h>
/* fact is a recursive function which takes an integer variable num and returns
an integer value */
int fact (int num)
{
/* Check if num value is equal to zero */
if (num==0)
/* Return the value 1 */
return 1;
/* Otherwise */
else
/* Return num * fact (num-1) value */
return (num * fact (num-1));
}
/* Main function */

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