寻找第K小值

#include<iostream.h>
int findValue(int k,int* a,int start,int end)
{
    
    int low=start;
    int high=end;
    int x=a[start];
    int flag=0;
    while (low!=high)
    {
        if (flag==0)
        {
            for (int j=high;j>=low;j--)
            {
                if (a[j]<x)
                {
                    a[low]=a[j];
                    high=j;
                    flag=1;
                    break;
                } 
                else
                {
                    if(j==low) high=low;
                }
            }
        } 
        else
        {
            for (int j=low;j<=high;j++)
            {
                if (a[j]>x)
                {
                    a[high]=a[j];
                    low=j;
                    flag=0;
                    break;
                } 
                else
                {
                    if(j==high) low=high;
                }
            }
        }
    }
    a[low]=x;
    if ((low-start+1)==k)
    {
        return a[low];
    }
    else if ((low-start+1)>k)
    {
        return findValue(k,a,start,low-1);
    }
    else
    {
        return findValue(k-(low-start)-1,a,low+1,end);
    }
    
}
void main()
{
    int a[]={1,2,3,4,5,6,7};
    cout<<findValue(4,a,0,6)<<endl;
}