链接：

题解：

1.先用partition函数，求得n/2的位置的排序

2.然后选取首尾指针（奇数选择1和length-1，偶数选择为1和length-2），进行swap交换

3.每次首指针每次+2，尾指针每次-2

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这段代码没有通过

class Solution {
public:
    /**
     * @param nums: A list of integers
     * @return: nothing
     */
    void wiggleSort(vector<int> &nums) {
        // write your code here
        if (nums.size() <= 1) {
            return;
        }
        int len = nums.size();
        kthLargestElement(len/2, nums);
        if (len % 2 == 0) {
            int left = 1;
            int right = nums.size()-2;
            while (left < right) {
                swap(nums[left], nums[right]);
                left += 2;
                right -= 2;
            }
        } else {
            int left = 1;
            int right = nums.size() - 1;
            while (left < right) {
                swap(nums[left], nums[right]);
                left += 2;
                right -= 2;
            }
        }
    }

private:
    int kthLargestElement(int k, vector<int> &nums) {
        cout << "k=" << k << endl;
        // write your code here
        if (nums.size() <= 0) {
            return 0;
        }
        int left = 0;
        int right = nums.size()-1;
        int mid = partition(nums, left, right);
        //cout << "mid=" << mid << endl;
        while (mid != k-1) {
            //cout << "mid=====" << mid << endl;
            if (mid > k) {
                right = mid;
            } else {
                left = mid;
            }
            mid = partition(nums, left, right);
        }
        return nums[mid];
    }
   
    int partition(std::vector<int>& nums, int left, int right) {
        int index = random() % (right-left+1);
        swap(nums[right], nums[left+index]);
        int nSmall = left - 1;
        for (; left < right; ++left) {
            if (nums[left] <= nums[right]) {
                ++nSmall;
                swap(nums[left], nums[nSmall]);
            }
        }
        ++nSmall;
        swap(nums[right], nums[nSmall]);
        cout << nSmall << " val=" << nums[nSmall] << endl;  
        return nSmall;
    }
};