查找数组中第k小的元素

#include <iostream>
#include<queue>
#include<vector>

using namespace std;


int KthNum(vector<int> num,int k)
{
    int size=num.size();
    if(size==0) return -1;
    priority_queue<int,vector<int>,less<int>> q;
    int i=0;
    while(i<size)
    {
        if(q.size()<k)
        {
            q.push(num[i++]);
        }
        else
        {
          if(q.top()>num[i])
          {
              q.pop();
              q.push(num[i]);
          }
          i++;
        }
    }

    return q.top();
}
int main()
{
    vector<int> num={3,6,1,7,2,4,8,9};
   int res= KthNum(num,4);
    cout<<res;
    return 0;
}