Lecture "Recursion", exercise 2

[essepuntato]

Define a recursive function def fib(n) that implements the algorithm to find the n^th Fibonacci number. In particular, if n is less than or equal to 0, then 0 is returned as a result. Otherwise, if n is equal to 1, then 1 is returned. Otherwise, return the sum of the same function called with n-1 and n-2 as input. Please accompany the function with the related test case.

[diegochillo]

def test_fib(n,expected):
  result=fib(n)
  return result==expected

def fib(n):
  if n<2:
    return n
  else:
    return fib(n-1)+fib(n-2)

print(test_fib(7,13))
print(test_fib(6,8))
print(test_fib(8,21))
print(test_fib(0,0))

[SusannaPinotti]

def test_fib(n, expected):
    result = fib(n)
    if expected == result:
        return True
    else:
        return False

def fib(n):
    if n <= 0:
        return 0
    elif n == 1:
        return 1
    else:
        return fib(n-1) + fib(n-2)

print(test_fib(7, 13)) #returns True
print(test_fib(1, 1)) #returns True
print(test_fib(19, 4181)) #returns Tru
```e 

[dbrembilla]

#test
def test(n, expected):
    return fib(n) == expected

#fibonacci
def fib(n):
    if n <= 0:
        return 0
    elif n < 2:
        return 1
    else:
        return fib(n-1) + fib(n-2)

print(test(10, 55)) # True
print(test(8, 21)) # True
print(test(1, 1)) # True

[gabrielefiorenza]

def test_fib(n,expected):
    result = fib(n)
    return result == expected

def fib(n):
    if n <= 0:
        return 0
    elif n ==1:
        return 1
    else:
        return fib(n-1) + fib(n-2)

print(test_fib(7,13)) #returns True
print(test_fib(1,1))#returns True
print(test_fib(0,0))#returns True

[AlessandraFa]

def test_fib(n, expected):
    return expected == fib(n)

def fib(n):
    if n <= 0:
        return 0
    if n == 1:
        return 1
    else:
        return fib(n-1)+fib(n-2)

print(test_fib(4, 3))  #True
print(test_fib(-2, 0)) #True
print(test_fib(1, 1))  #True

[IlaRoss]

#tests
def test_fibonacci(n, expected):
    result = fibonacci(n)
    if result == expected:
        return True
    else:
        return False

#algorithm with recursion
def fibonacci(n):
    if n == 1:
        return 1
    if n <= 0:
        return 0
    else:
        return fibonacci(n-1) + fibonacci(n-2)

#test runs
a = test_fibonacci(8, 21)
b = test_fibonacci(5, 5)
c = test_fibonacci(1, 1)
d = test_fibonacci(-3, 0)

print(a)
print(b)
print(c)
print(d)

[ChiaraCati]

def test_fib(n, expected):
    result = fib(n)
    if result == expected:
        return True
    else:
        return False

def fib(n):
    if n <= 0:
        return 0
    elif n == 1:
        return 1
    else:
        return fib(n-1) + fib(n-2)

print(test_fib(-5, 0))
print(test_fib(0,0))
print(test_fib(1,1))
print(test_fib(2,1))
print(test_fib(3,2))
print(test_fib(4,3))

[AleRosae]

def test_fin(n, expected):
    return expected == fin(n)

def fin(n):
    if n <= 0:
        return 0
    elif n == 1:
        return 1
    else:
        return fin(n-1) + fin(n-2)

print(test_fin(7,13))
print(test_fin(1,1))
print(test_fin(-7,0))

[yunglong28]

def test_fib (n, expected):
    result = fib(n)
    if result == expected:
        return True
    else:
        return False

def fib (n):
    if n <= 0:
        return 0
    elif n == 1:
        return 1
    else:
        return fib(n-1) + fib(n-2)

print(test_fib(7, 13))

[edoardodalborgo]

def test_fib(n, expected):
    return fib(n) == expected

def fib(n):
    if n < 2:
        return n
    else:
        return fib(n - 1) + fib(n - 2)

print(test_fib(3, 2))
print(test_fib(5, 5))
print(test_fib(10, 55))

[fcagnola]

# Define a recursive function def fib(n) that implements the algorithm to find the nth Fibonacci number.
# In particular, if n is less than or equal to 0, then 0 is returned as a result. Otherwise, if n is equal to 1,
# then 1 is returned. Otherwise, return the sum of the same function called with n-1 and n-2 as input.
# Please accompany the function with the related test case.

from test import test_1_parameter

def fib(number):
    if number <= 0:
        return 0
    elif number == 1:
        return 1
    else:
        return fib(number-1) + fib(number-2)

print(test_1_parameter(fib,3,2)) # returns True
print(test_1_parameter(fib,7,13)) # returns True

[SofiBar]

def test_fib(n, expected):
    return fib(n) == expected

def fib(n):
    if n <= 0:
        return 0
    elif n == 1:
        return 1
    else:
        return fib(n-1)+fib(n-2)

print(test_fib(4, 3))
print(test_fib(6, 8))
print(test_fib(0, 0))

[giorgiasampo]

def test_fib(n,expected):
    result = fib(n)
    return result == expected

def fib(n):
    if n <= 0:
        return 0
    else:
        if n == 1:
            return 1
        else:
            return fib(n-1)+fib(n-2)

print (test_fib(0,0))
print (test_fib(1,1))
print (test_fib(4,3))
print (test_fib(6,8))

[vanessabonanno]

def test_fib(n, expected):
    result = fib(n)
    if result == expected:
        return True
    else:
        return False

def fib(n):
    if n <= 0:
        return 0
    elif n == 1:
        return 1
    elif n > 1:
        return fib(n - 1) + fib(n - 2)
    else:
        return "Wrong input"

print(fib(7))           # 13
print(fib(4))           # 3
print(test_fib(7, 13))  # True
print(test_fib(1, 1))   # True
print(test_fib(0, 0))   # True
print(test_fib(4, 4))   # False

#  With big inputs the recursion may take a long time.
#  PythonTutor shows the following alert with input = 77:
#  "Stopped since stack has 30 functions on it.
#   You may have infinite recursion"

[laurentfintoni]

def test_fib(n, expected):
    result = fib(n)
    if result == expected:
        return True
    else: 
        return False 

def fib(n):
    if n == 0:
        return 0
    elif n == 1:
        return 1
    else:
        return fib(n - 1) + fib(n-2)

print(test_fib(4, 3))
print(test_fib(1, 1))
print(test_fib(0, 0))

[AlessandroBertozzi]

# Test case for the algorithm
def test_fib(n, expected):
    result = fib(n)
    if expected == result:
        return True
    else:
        return False

# Code of the algorithm
def fib(n):
    if n <= 0:
        return 0
    elif n == 1:
        return 1
    else:
        return fib(n - 1) + fib(n - 2)

print(test_fib(7, 13))
print(test_fib(1, 1))
print((test_fib(0, 0)))

[essepuntato]

Hi all,

Thanks for your solution. In your tests, can I suggest to add also an execution with negative input, e.g. fib(-4)? Can you try to see if your function still behaves as expected (i.e. returning 0 in these cases)?

[dbrembilla]

Hi all,

Thanks for your solution. In your tests, can I suggest to add also an execution with negative input, e.g. fib(-4)? Can you try to see if your function still behaves as expected (i.e. returning 0 in these cases)?

Hello,

In my case it returned 0 with negative numbers, as expected

[diegochillo]

Hi all,

Thanks for your solution. In your tests, can I suggest to add also an execution with negative input, e.g. fib(-4)? Can you try to see if your function still behaves as expected (i.e. returning 0 in these cases)?

My function didn't work well with negatives. Here is a reviewed version:

def test_fib(n,expected):
  result=fib(n)
  return result==expected

def fib(n):
  if 0<=n<2:
    return n
  elif n>1:
    return fib(n-1)+fib(n-2)
  return 0

# Test cases
print(test_fib(7,13))
print(test_fib(6,8))
print(test_fib(8,21))
print(test_fib(0,0))
print(test_fib(-4,0))

[GiuliaMenna]

def test_fib(n, expected):
    result = fib(n)
    if expected == result:
        return True
    else:
        return False

def fib(n):
    if n <= 0:
        return 0
    if n == 1:
        return 1
    else:
        return fib(n-1) + fib(n-2)
    return result

print(test_fib(0,0))
print(test_fib(1,1))
print(test_fib(7,13))