• Time:O(n)
• Space:O(1)

## C++

``````class Solution {
public:
void wiggleSort(vector<int>& nums) {
// 1. if i is even, then nums[i] <= nums[i - 1]
// 2. if i is odd, then nums[i] >= nums[i - 1]
for (int i = 1; i < nums.size(); ++i)
if ((!(i & 1) && nums[i] > nums[i - 1]) ||
((i & 1) && nums[i] < nums[i - 1]))
swap(nums[i], nums[i - 1]);
}
};
``````

## JAVA

``````class Solution {
public void wiggleSort(int[] nums) {
// 1. if i is even, then nums[i] <= nums[i - 1]
// 2. if i is odd, then nums[i] >= nums[i - 1]
for (int i = 1; i < nums.length; ++i)
if ((i % 2 == 0 && nums[i] > nums[i - 1]) || (i % 2 == 1 && nums[i] < nums[i - 1]))
swap(nums, i, i - 1);
}

private void swap(int[] nums, int i, int j) {
final int temp = nums[i];
nums[i] = nums[j];
nums[j] = temp;
}
}
``````

## Python

``````class Solution:
def wiggleSort(self, nums: List[int]) -> None:
# 1. if i is even, then nums[i] <= nums[i - 1]
# 2. if i is odd, then nums[i] >= nums[i - 1]
for i in range(1, len(nums)):
if not (i & 1) and nums[i] > nums[i - 1] or \
(i & 1) and nums[i] < nums[i - 1]:
nums[i], nums[i - 1] = nums[i - 1], nums[i]
``````