Equal Sides Of An Array
链接： https://www.codewars.com/kata/5679aa472b8f57fb8c000047
题目介绍
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.
参考答案
一句话代码解决方案，我的提交：
const findEvenIndex = a => a.findIndex((e, i) =>
a.slice(0, i).reduce((r, c) => r + c, 0) === a.slice(i + 1).reduce((r, c) => r + c, 0));
拓展阅读
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