/**
* Runtime: 84 ms, faster than 38.21% of JavaScript online submissions for Find Pivot Index.
Memory Usage: 40 MB, less than 50.00% of JavaScript online submissions for Find Pivot Index.
 */
const pivotIndex = nums => {
    let leftMap = getSumMap(nums)
    let rightMap = getSumMap(nums.reverse())
    let result = -1
    Object.keys(leftMap).some((index) => {
        if (leftMap[index] === rightMap[nums.length - 1 - index]) {
            result = index
            return true
        }
        return false
    })
    return result
};

function getSumMap(nums) {
    let map = {}
    map[0] = 0
    nums.reduce((accumulator, currentValue, index) => {
        let sum = accumulator + currentValue
        map[index + 1] = sum
        return sum
    }, 0)
    return map
}