数组中的第K个最大元素

class Solution {
public:
    int findKthLargest(vector<int>& nums, int k) {
        int index=getKthindex(nums,k,0,nums.size()-1);
        return nums[index];
    }
    
    int getKthindex(vector<int>&a,int k,int lo,int hi){
        int mi=getPartion(a,lo,hi);
        if(mi==a.size()-k)return mi;
        else if(mi<a.size()-k)return getKthindex(a,k,mi+1,hi);
        else{
            return getKthindex(a,k,lo,mi-1);
        }
    }
    
    int getPartion(vector<int>&a,int lo,int hi){
        int pivot=a[lo];
        while(lo<hi){
            while(lo<hi&&pivot<=a[hi])hi--;
            swap(a[lo],a[hi]);
            while(lo<hi&&pivot>=a[lo])lo++;
            swap(a[lo],a[hi]);
        }
        return lo;
    }
};