CODEWITHSUNDEEP
pythonrecursion
ZεԺ
ZεԺ

Reputation: 221

My python recursive function won't return and exceeds maximum recursive depth

I simply do not understand why this is not returning the value and stopping the recursion. I have tried everything but it seems to just keep on going no matter what I do. I am trying to get the program to get the loop to compare the first two values of the list if they are the same return that it was the first value. If they were not, add the first and second values of each list and compare, etc etc until it reaches the end of the list. If the sum of the values in each list never equal each other at any point then return 0.

It is supposed to take three inputs:

  1. A single integer defining the length of the next two inputs
  2. First set of input data
  3. Second set of input data

Ex input

3

1 3 3

2 2 2

It should output a single number. In the case of the example data, it should output 2 because the sum of the lists equalled at the second value.

N = int(input())
s1 = input().split()
s2 = input().split()
count = 0

def func1(x,y):
        if x == y:
            return(count)
        elif (N - 1) == count:
            return(0)
        else:
            count + 1
            return(func1(x + int(s1[count]), y + int(s2[count])))

days = func1(int(s1[0]),int(s2[0]))
print(days)

I am sorry in advance if I really messed up the formatting or made some dumb mistake, I am pretty new to programming and I have never posted on here before. Thanks in advance :)

Upvotes: 0

Views: 62

Answers (2)

AKX
AKX

Reputation: 169051

To answer "How would you go about solving this problem then" – If I understood the problem correctly, the aim is to find the index where the "running total" of the two lists is the same. If so,

def func1(s1, s2):
    total_a = 0
    total_b = 0
    for i, (a, b) in enumerate(zip(s1, s2)):
        total_a += a
        total_b += b
        if total_a == total_b:
            return i
    return 0


print(func1([1, 3, 3], [2, 2, 2]))

does the trick. (I've elided the input bits here – this function just works with two lists of integers.)

Upvotes: 0

bereal
bereal

Reputation: 34282

The problem is that you never actually update the variable count. However, just writing:

count += 1

is not going to work either without declaring the variable global:

def func1(x, y):
    global count
    ....

That said, global variables increase code complexity and break re-enterability, i.e. the same function can no longer be called twice, not to mention about concurrency. A much cleaner way is to make count a function argument, it will look like this (the code not tested and is here for illustration only):

N = int(input())
s1 = [int(c) for c in input().split()]
s2 = [int(c) for c in input().split()]

def func1(x, y, count=0):
    if x == y:
        return count
    elif count == N - 1:
        return 0
    else:
        return(func1(x + s1[count], y + s2[count]), count + 1)

days = func1(int(s1[0]),int(s2[0]))
print(days)

Upvotes: 1

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