189. 轮转数组
给你一个数组，将数组中的元素向右轮转 k **个位置，其中 k **是非负数。
let length = nums.count
if length == 1 {
return
}
let k1 = k % nums.count
reverse(&nums, 0, length - 1)
reverse(&nums, 0, k1 - 1)
reverse(&nums, k1, length - 1)
}
func reverse (_ nums: inout[Int], _ start: Int, _ end: Int){
var start = start
var end = end
while start < end {
let temp = nums[start]
nums[start] = nums[end]
nums[end] = temp
start += 1
end -= 1
}
}
