faster implementation of sum ( for Codility test )

Question

How can the following simple implementation of sum be faster?

private long sum( int [] a, int begin, int end ) {
    if( a == null   ) {
        ret         


        

Answer 1

This may be old, but here is solution in Golang with 100% pass rate:

package solution

func Solution(A []int) int {
    // write your code in Go 1.4
    var left int64
    var right int64
    var equi int

    equi = -1
    if len(A) == 0 {
        return equi
    }

    left = 0
    for _, el := range A {
        right += int64(el)
    }

    for i, el := range A {
        right -= int64(el)
        if left == right {
            equi = i
        }
        left += int64(el)
    }

    return equi
}