题目:
题解:
class Solution {
public:
int partitionAroundPivot(int left, int right, int pivot, vector<int> &nums) {
int pivotValue = nums[pivot];
int newPivot = left;
swap(nums[pivot], nums[right]);
for (int i = left; i < right; ++i) {
if (nums[i] > pivotValue) {
swap(nums[i], nums[newPivot++]);
}
}
swap(nums[right], nums[newPivot]);
return newPivot;
}
int findKthLargest(vector<int> &nums, int k) {
int left = 0, right = nums.size() - 1;
default_random_engine gen((random_device())());
while (left <= right) {
uniform_int_distribution<int> dis(left, right);
int pivot = dis(gen);
int newPivot = partitionAroundPivot(left, right, pivot, nums);
if (newPivot == k - 1) {
return nums[newPivot];
} else if (newPivot > k - 1) {
right = newPivot - 1;
} else {
left = newPivot + 1;
}
}
return nums[k - 1];
}
inline int transAddress(int i, int n) {
return (2 * n - 2 * i - 1) % (n | 1);
}
void wiggleSort(vector<int>& nums) {
int n = nums.size();
int x = (n + 1) / 2;
int mid = x - 1;
int target = findKthLargest(nums, n - mid);
for (int k = 0, i = 0, j = n - 1; k <= j; k++) {
if (nums[transAddress(k, n)] > target) {
while (j > k && nums[transAddress(j, n)] > target) {
j--;
}
swap(nums[transAddress(k, n)], nums[transAddress(j--, n)]);
}
if (nums[transAddress(k, n)] < target) {
swap(nums[transAddress(k, n)], nums[transAddress(i++, n)]);
}
}
}
};