[ . ] python

def reverse(n):
    if n == 0:
        return
    else:
        print(n)
        reverse(n-1)
        
        
reverse(5)

5
4
3
2
1

def print_no(n):
  if n == 0:
    return
  print_no(n - 1)
  print(n)

print_no(10)

1
2
3
4
5
6
7
8
9
10

def sum_of_int(n):
    if n == 1:
        return 1
    else:
        return n + sum_of_int(n-1)
    
print(sum_of_int(5))

15

def factorial(n):
    if n == 0:
        return 1
    else:
        return n * factorial(n - 1)
factorial(5)

120

def fibonacci_series(n):
    if n <= 1:
        return n
    else:
        return fibonacci_series(n-1) + fibonacci_series(n-2)
    
fibonacci_series(5)
     

5

def add(a, b):
  if b == 0:
    return a
  else:
    return add(a + 1, b - 1)

print(add(1, 2))

3

def reverse_number(number,a):
    if number == 0:
        return a
    else:
        a = 10 * a + number % 10
        return reverse_number(number // 10,a)
a = 0
print(reverse_number(12345,a))

54321

def gcd(a, b):
    if b == 0:
        return a
    else:
        return gcd(b, a % b)
print(gcd(12, 18))

6

def fibonacci(n):
    if n <= 1:
        return n
    else:
        return fibonacci(n-1) + fibonacci(n-2)
for i in range(7):
    print(fibonacci(i))

0
1
1
2
3
5
8

def even_odd(n):
    if n == 1:
        return "odd"
    if n == 0:
        return "even"
    else:
        return even_odd(n-2)
    
c = even_odd(10)
print(c)

even

def even_odd(n):
    if n == 1:
        return 1
    if n == 0:
        return 0
    else:
        return even_odd(n-2)
    
c = even_odd(10)
if c == 1:
    print("odd")
else: 
    print("even")

even

def check_a(string):
    if len(string) == 0:
        return False
    elif string[0] == 'a':
        return True
    else:
        return check_a(string[1:])
string = "hello world"
if check_a(string):
    print("present")
else:
    print("not present")

not present