Kth-largest

class Solution {
public:
    int QuickSortIndex(vector<int>& nums, int i, int j){
        int pivot = i;

        while(i <= j){
            while(i<nums.size() && nums[i] <= nums[pivot]){
                i++;
            }

            while(j >= 0 && nums[j] > nums[pivot]){
                j--;
            }

            if(i <j ){
                swap(nums[i], nums[j]);
            }
        }

        swap(nums[j], nums[pivot]);
        return j;
    }


    int findKthLargest(vector<int>& nums, int k) {
        int i=0, j=nums.size()-1;
        while(i<=j){
            int pivot = QuickSortIndex(nums, i, j);
            if(pivot == nums.size()- k){
                return nums[pivot];
            }

            if(pivot > nums.size() - k){
                j = pivot - 1;
            }
            else{
                i = pivot + 1;
            }
        }

        return -1;
    }
};