背模板

C++ 代码

#include<iostream>
using namespace std;
const int N = 1e6 + 10;
int q[N];
void swap_q(int q[], int x, int y)
{
    if(x== y)   return;
    int z = q[x + y >> 1], i = x - 1, j = y + 1;
    while(i < j)
    {
        do  i++; while(q[i] < z);
        do  j--; while(q[j] > z);
        if(i < j)   swap(q[i], q[j]);
    }
    swap_q(q, x, j);
    swap_q(q, j + 1, y);
}
int main()
{
    int n, k;
    cin >> n >> k;
    for(int i = 0; i < n; i++)  cin >> q[i];
    swap_q(q, 0 , n - 1);
    cout << q[k - 1];
    return 0;
}

Java 代码

import java.util.Scanner;
public class Main
{
    static int N = 1000010;
    static int q[] = new int[N];
    public static void main(String[] args)
    {
        Scanner in = new Scanner(System.in);
        int n, k;
        n = in.nextInt();
        k = in.nextInt();
        for(int i = 0; i < n; i++)  q[i] = in.nextInt();
        swap_a(q, 0, n - 1);
        System.out.println(q[k - 1]);
    }
    public static void swap_a(int q[], int x, int y)
    {
        if(x == y)  return;
        int z = q[(x + y) / 2], i = x - 1, j = y + 1;
        while(i < j)
        {
            do  i++;    while(q[i] < z);
            do  j--;    while(q[j] > z);
            if(i < j)
            {
                q[i] = q[i] + q[j];
                q[j] = q[i] - q[j];
                q[i] = q[i] - q[j];
            }
        }
        swap_a(q, x, j);
        swap_a(q, j + 1, y);
    }
}