insertElement deleteElement

func insertElement(arr []int, x int, pos int) []int {
    arr = append(arr, 0)
    copy(arr[pos+1:], arr[pos:])
    arr[pos] = x
    return arr
}

func deleteElement(arr []int, pos int) []int {
    copy(arr[pos:], arr[pos+1:])
    return arr[:len(arr)-1]
}