查找无序数组中第K大的数

#include <iostream>
#include <algorithm>
#include <cstdio>5
using namespace std;
int findK(int left, int right, int arr[], int k) {
    if(left >= right) return arr[left];
    int first = left, last = right;
    int key = arr[first];
    while(first < last) {
        while(first < last && arr[last] >= key) last--;
        arr[first] = arr[last];
        while(first < last && arr[first] <= key) first++;
        arr[last] = arr[first];
    }
    arr[first] = key;
    if(first == k) return arr[k];
    else {
        if(first > k) return findK(left, first, arr, k);
        else return findK(first+1, right, arr, k);
    }
}
int main()
{
    int n;
    int arr[1000];

    scanf("%d", &n);
    for(int i = 1; i <= n; i++) cin >>arr[i];
    int k;
    cin >> k;
    int num = findK(1, n, arr, k);
    cout << num << endl;
    return 0;
}