1. A recursive function is a function that calls itself, either directly or indirectly. It is related to mathematical induction. 2. Examples of inherently recursive functions include calculating factorials and finding terms in the Fibonacci series recursively. 3. Recursive functions require a base or stop condition to return the final value, otherwise the function will keep calling itself indefinitely. Pseudocode and C code examples are provided to find factorials, sum of natural numbers, and Fibonacci series recursively.

1. SESSION – 20
RECURSIVE FUNCTION
Session Outcome:
1. Understanding Recursive Functions
2. Examples Of Recursive Functions

2. Recursive Functions
• Recursive function is closely related to
mathematical induction
• Recursive function is a function that calls itself
• Every Recursive function will have exit or stop
condition
– other wise the recursive function will keep on
calling itself
Wednesday, June 10, 2020
For suggestions or queries contact
drkrk@kluniversity.in

3. Inherently recursive functions
5!
5*4!
4*3!
3*2!
2*1!
1
5!
5*4!
4*3!
3*2!
2*1!
1
Final value=120
1
2!=2*1=2 returned
3!=3*2=6 returned
4!=4*6=24 returned
5!=5*24=120 returned

4. Finding Factorial Recursively
Wednesday, June 10, 2020
For suggestions or queries contact
drkrk@kluniversity.in
fact(5)
5*fact(4)
4*fact(3)
3*fact(2)
2*fact(1)1
2
6
24
120

5. Finding Factorial Recursively
𝑓𝑎𝑐𝑡 𝑛 =
1 𝑖𝑓 𝑛 == 0 𝑜𝑟 𝑛 == 1
𝑛 ∗ 𝑓𝑎𝑐𝑡 𝑛 − 1 𝑖𝑓 𝑛 > 1
Wednesday, June 10, 2020
For suggestions or queries contact
drkrk@kluniversity.in
Corresponding Recursive Function
int fact(int n)
{
if(n ==1 || n ==0)
return 1;
else
return n*fact(n-1);
}

6. Finding Factorial Recursively
Complete program is:
#include<stdio.h>
int fact(int);
main()
{
int n;
scanf("%d",&n);
printf("%d",fact(n));
}
int fact(int n)
{
if(n ==1 || n ==0)
return 1;
else
return n*fact(n-1);
}

7. Sum of Natural Numbers Recursively
Wednesday, June 10, 2020
For suggestions or queries contact
drkrk@kluniversity.in
𝑠𝑢𝑚 𝑛 =
1 𝑖𝑓 𝑛 == 1
𝑛 + 𝑠𝑢𝑚 𝑛 − 1 𝑖𝑓 𝑛 > 1
Corresponding Recursive Function
int sum(int n)
{
if(n ==1)
return 1;
else
return n + sum(n-1);
}

8. Finding nth term in Fibonacci Series Recursively
𝑓𝑖𝑏 𝑛 =
0 𝑖𝑓 𝑛 == 0
1 𝑖𝑓 𝑛 == 1
𝑓𝑖𝑏 𝑛 − 1 + 𝑓𝑖𝑏 𝑛 − 2 𝑖𝑓 𝑛 > 1
Corresponding Recursive Function
int fib(int n)
{
if( n ==0)
return 0;
if( n ==1)
return 1;
else
return fib(n-1)*fib(n-2);
}