Recursive functions in C

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);
}