Given an unsorted array nums, reorder it in-place such that nums[0] <= nums[1] >= nums[2] <= nums[3]....
For example, given nums = [3, 5, 2, 1, 6, 4], one possible answer is [1, 6, 2, 5, 3, 4].
贪心，数学归纳法很容易证明出来。
1 class Solution { 2 public: 3 void wiggleSort(vector<int>& nums) { 4 int flag = 1; 5 for (int i = 1; i < nums.size(); ++i) { 6 if (nums[i] * flag < nums[i-1] * flag) 7 swap(nums[i], nums[i-1]); 8 flag = -flag; 9 } 10 } 11 };