When `i`

is odd, let nums[i] > mums[i - 1]. When `i`

is even, let nums[i] < nums[i - 1]. Use `x`

and `y`

to reduce number of reads.

```
def wiggleSort(self, nums):
for i in range(1, len(nums)):
x, y = nums[i - 1], nums[i]
if (i & 1) ^ (x < y): nums[i - 1], nums[i] = y, x
```