lc 数组中的第K个最大元素

链接：https://leetcode-cn.com/problems/kth-largest-element-in-an-array/

代码：

class Solution {
public:
    int findKthLargest(vector<int>& nums, int k) {
        k--;
        return solve(nums, 0, nums.size()-1, k);
    }
    int solve(vector<int>& nums, int low, int high, int k) {
        int privot = nums[low];
        int ll = low;
        int hh = high;
        int index = partition(nums, low, high);
        if(index == k) return nums[k];
        else if(k < index) {
            return solve(nums, ll, index-1, k);
        }
        else {
            return solve(nums, index+1, hh, k);
        }
    }
    int partition(vector<int>& nums, int low, int high) {
        if(low == high) return low;
        int privot = nums[low];
        while(low < high) {
            while(low < high && nums[high] <= privot) high--;
            nums[low] = nums[high];
            while(low < high && nums[low] >= privot) low++;
            nums[high] = nums[low];
            // cout << "======" << endl;
        }
        nums[low] = privot;
        return low;
    }
};

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思路：参考快排partition 思想，再递归，一直到 partition 返回的坐标是 k，复杂度是O(n)，因为费时操作是 partition。