====== TopK.java ======
<code java>
public class TopK {

    private int [] buffer;
    private int k;
    private int len;

    public TopK(int sk) {
        k = sk;
        len = 0;
        buffer = new int[k];
    }

    public int getNumKept() { return len; }

    public int get(int i) { return buffer[i]; }

    public void add(int x) {
        if(k==0)
            return;
        if(len<k) {
            buffer[len] = x;
            len++;
        } else {
            int min = buffer[0], mi = 0;
            for(int i = 1; i<len; i++)
                if(buffer[i]<min) {
                    min = buffer[i];
                    mi = i;
                }
            if(min<x) {
                buffer[mi] = x;
            }
        }
    }
}
</code>