去重且排序

func (a Values) Deduplicate() Values {
    if len(a) <= 1 {
        return a
    }

    // See if we're already sorted and deduped
    var needSort bool
    for i := 1; i < len(a); i++ {
        if a[i-1].UnixNano() >= a[i].UnixNano() {
            needSort = true
            break
        }
    }

    if !needSort {
        return a
    }

    sort.Stable(a)
    //双指针去重
    var i int
    for j := 1; j < len(a); j++ {
        v := a[j]
        if v.UnixNano() != a[i].UnixNano() {
            i++
        }
        a[i] = v

    }
    return a[:i+1]
}