exercise week1

#include <iostream>
#include<algorithm>
#include <vector>
 
using namespace std;
 
const int N = 100010;
int n, k;
int q[N];
 
int quick_sort(int l, int r, int k) {
    if (l == r) return q[l];
    int i = l - 1, j = r + 1, x = q[l];
    while (i < j) {
        while (q[++i] < x);
        while (q[--j] > x);
        swap(q[i], q[j]);
    }
    int sl = j - i + 1;
    //k小于左区间的长度 那么这个数在左区间中
    if (k <= sl) return quick_sort(l, j, k);
  	//否则 第k小的数是右区间的k-sl小的数
    return quick_sort(j + 1, r, k - sl);
}
 
int main() {
    cin >> n >> k;
    for (int i = 0; i < n; i++) cin >> q[i];
    cout << quick_sort(0, n - 1, k) << endl;
    return 0;
}