leetcode-Kth Largest Element in an Array-215

 1 class Solution {
 2 public:
 3     void quick(vector<int> &a,int low,int high,int k){
 4         int i=low,j=high-1;
 5         int tmp=a[i];
 6         while(i<j){
 7             while(i<j&&a[j]>=tmp) j--;
 8             a[i]=a[j];
 9             while(i<j&&a[i]<=tmp) i++;
10             a[j]=a[i];
11         }
12         a[i]=tmp;
13         if(i==a.size()-k) return;
14         if(i>low) quick(a,low,i,k);
15         if(i+1<high) quick(a,i+1,high,k);
16     }
17     int findKthLargest(vector<int>& nums, int k) {
18         if(nums.size()<k) return -1;
19         quick(nums,0,nums.size(),k);
20         return nums[nums.size()-k];
21     }
22 };