Kata's link: ⛵Equal Sides Of An Array

You are going to be given an array of integers. Your job is to take that array and find an index N where the sum of the integers to the left of N is equal to the sum of the integers to the right of N. If there is no index that would make this happen, return -1.

For example:

Let's say you are given the array {1,2,3,4,3,2,1}: Your function will return the index 3, because at the 3rd position of the array, the sum of left side of the index ({1,2,3}) and the sum of the right side of the index ({3,2,1}) both equal 6.

Let's look at another one. You are given the array {1,100,50,-51,1,1}: Your function will return the index 1, because at the 1st position of the array, the sum of left side of the index ({1}) and the sum of the right side of the index ({50,-51,1,1}) both equal 1.

Last one: You are given the array {20,10,-80,10,10,15,35} At index 0 the left side is {} The right side is {10,-80,10,10,15,35} They both are equal to 0 when added. (Empty arrays are equal to 0 in this problem) Index 0 is the place where the left side and right side are equal.

Note: Please remember that in most programming/scripting languages the index of an array starts at 0.

Input:

An integer array of length 0 < arr < 1000. The numbers in the array can be any integer positive or negative.

Output:

The lowest index N where the side to the left of N is equal to the side to the right of N. If you do not find an index that fits these rules, then you will return -1.

Note:

If you are given an array with multiple answers, return the lowest correct index. An empty array should be treated like a 0 in this problem.

Best Practices

Py First:

def find_even_index(arr):
    for i in range(len(arr)):
        if sum(arr[:i]) == sum(arr[i+1:]):
            return i
    return -1

Py Second:

find_even_index = lambda arr: next((i for i, __ in enumerate(arr) if sum(arr[:i]) == sum(arr[i+1:])), -1)

Py Third:

def find_even_index(arr):
    r = [i for i in range(len(arr)) if sum(arr[0:i]) == sum(arr[i+1:])]
    return r[0] if r else -1