Recursive Function

Enter your email address:

मैल पर फीड बर्नर से प्राप्त लिंक Verify करे

Computer Science 

( Class XII Sc ) 

( Subject Code 083)

Recursion

When a function call itself repeatedly , function is called recursive function and process in called recursion.


Direct recursion: When a function call itself directly from its body
def A():
      A()

Indirect recursion: When a function call another function, which call its caller fuction

def A():                def B():
       B()                      A():

Infinite recursion :  When a function call itself  repeatedly call again and again endlessly. It happens when base condition is not given or not reachable

One advantage and one disadvantage of recursion over iteration:
Advantage: Recursion makes code short and simple
Disadvantage:  Recursion is slower then iteration due to overhead of multiple function calling and  maintaining stack  of it

#factorial using recursion
def fact(x):

    if(x==1):

        return 1

    else:

        return x*fact(x-1)

# sum of n natural numbers using recursion function

def sum(n):

    if(n<=1):

        return n

    else:

        return n+sum(n-1)

n=int(input("enter a number"))

print("sum of n natural numbers",sum(n))

sum(6)
6+sum(5)
6+5+sum(4)
6+5+4+sum(3)
6+5+4+3+sum(2)
6+5+4+3+2+sum(1)
6+5+4+3+2+1
=21

#Calculate power of an input  number using recursion

def power(x,n):

    if(n==0):

        return 1

    else:

        return x*power(x,n-1)

x=int (input("Enter value of x") )

n=int (input("Enter value of n") )

print(power(x,n))

#fibonacci series using recursion

def febo(n):

    if(n<=1):

        return n

    else:

        return(febo(n-1)+febo(n-2))

n=int(input("how many terms required for series"))

for i in range(n):

    print(febo(i))

#sum of squares using recursion

def sum(n):

    if n==1:

        return 1

    else:

        return n**2+sum(n-1)

print(sum(5))

#binary search in a list
# values must be sort before binary search

def binarySearch(arr, low, high, x): 
      while low <= high: 
        mid = int((low + high)/2)
         
        # Check if x is present at mid 
        if arr[mid] == x: 
            return mid 
  
        # If x is greater, ignore left half 
        elif arr[mid] < x: 
            low = mid + 1
  
        # If x is smaller, ignore right half 
        else: 
            high = mid - 1

    else:
        return -1

arr=[22,33,56,78,85,92,97]
pos=binarySearch(arr,0,6,78)
if(pos==-1):
    print("item not found")
else:
    print("item present at",pos)

# binary search using recursion 
def binarySearch (arr, low, high, x):

  if high >=low :

       mid = int((low + high)/2)

 

  if arr[mid]== x:

        return mid

 

  elif arr[mid]> x:

        return binarySearch(arr, low, mid-1, x)

  else:

       return binarySearch(arr, mid+1, high, x)

  
else:

  return -1