求区间第k大的值

#include <iostream>

using namespace std;

int part(int a[], int i, int j)
{
    int tmp = a[i];

    if(i < j)
    {
        while(i < j)
        {
            while(i<j && a[j]>=tmp)
                j--;
            if(i < j)
                a[i] = a[j];
            while(i<j && a[i]<tmp)
                i++;
            if(i < j)
                a[j] = a[i];
        }
        a[i] = tmp;
        return i;
    }
}

int check(int a[], int i, int j, int k)
{
    int m = part(a, i, j);
    if(k == m-i+1)
        return a[m];
    else if(k < m-i+1)
        return check(a, i, m-1, k);
    else
        return check(a, m+1, j, k-(m-i+1));
}

int main()
{

    int a[9] = {3,2,6,5,7,8,9,1,0};

    int k = 0;

    cout << check(a, 0, 8, 9-k)<< endl;
    return 0;
}