Equilibrium Algorithm Answer in Swift 3

EquilibriumIndex.swift

import Foundation

public func equilibriumIndex(_ A : inout [Int]) -> Int {

	var rightSum = A.reduce(0, +)
	var leftSum = 0

	for (index, element) in A.enumerated() {
		rightSum -= element
		guard rightSum != leftSum else { return index }
		leftSum += element
	}

	return -1
}

public func allEquilibriumIndexs(_ A : inout [Int]) -> [Int] {

	var all: [Int] = []

	var rightSum = A.reduce(0, +)
	var leftSum = 0

	for (index, element) in A.enumerated() {
		rightSum -= element

		if rightSum == leftSum {
			all.append(index)
		}

		leftSum += element
	}

	return all
}

var test0 = [-1, 3, -4, 5, 1, -6, 2, 1]
var test1 = [-7, 1, 5, 2, -4, 3, 0]
var test2 = [-156, 138, -2, -156, 138, -156, -2]

for var test in [test0, test1, test2] {
	print("solution \(equilibriumIndex(&test))")
	print("allSolutions \(allEquilibriumIndexs(&test))")
}