Find contiguous integers with a given sum

Question

Introduction

This question was asked in a technical interview, I am looking for some feedback on my solution.

Given a list of integers and a number K, return which contiguous elements of the list sum to K. For example, if the list is [1, 2, 3, 4, 5] and K is 9, then it should return [2, 3, 4].

The Ask

My solution works with my test cases, but I would like feedback on how others would approach the problem and where my code could be altered to improve efficiency and runtime. Currently, I have a nested for loop and I believe my solution is O(n²).

Solution

def contigSum(nums, k):

    for i, num in enumerate(nums): 
        accum = 0
        result = [] 
        # print(f'Current index = {i}')
        # print(f'Starting value = {num}')

        for val in nums[i:len(nums)]:
            # print(f'accum = {accum}')
            result.append(val)
            # print(f'accum = {accum} + {val}')
            accum += val 

            if accum == k: 
                print(f'{result} = {k}')
                return 0
            # else:
                # print(f'accum = {accum}')

    print('No match found')
    return 1

Test Cases

nums0 = []
k0 = None 
contigSum(nums0, k0)

nums6 = [1, 2, 3]
k6 = 99
contigSum(nums6, k6)

nums1 = [1, 2, 3, 4, 5]
k1 = 9
contigSum(nums1, k1)

nums2 = [-1, -2, -3]
k2 = -6
contigSum(nums2, k2)

nums4 = [5, 2, 6, 11, 284, -25, -2, 11]
k4 = 9 
contigSum(nums4, k4)

nums5 = [10, 9, 7, 6, 5, 4, 3, 2 ,1]
k5 = 20 
contigSum(nums5, k5)

Answer 1

Unused code

for i, num in enumerate(nums):, the i variable is used in your commented code, but commented code shouldn't exist, so i shouldn't exist either.

To come back on the commented code, I hope you didn't submit your solution with these comments as this is a (in my opinion) very bad practice. What does commented code mean after all? These comments could all be replaced by any debugging tool.

Running time

I believe your solution is actually running on \$O(n*\log(n))\$ time as the nested loop doesn't restart at index 1 every time it runs (which is a good thing). Seems like this is wrong.

Code structure

Usually, in an interview question code structure is pretty important. Right now you have one method that does everything. You should at least have a method that returns your result and one that prints it. Something like :

def main():
    nums = ...
    k = ...
    print(contigSum(nums, k))

def contigSum(nums, k):
    ...

and contigSum should return the result, not print it.