如何从预扫描中构建霍夫曼树？

Question

我对如何从预扫描中构建霍夫曼树感到有些困惑。我对标题进行了类似于here

的说明

但是我不确定如何读取扫描并构建树，我的扫描看起来像这样

01a001c1b001f1e1d＃（＃标签用于中断循环）

这是我尝试构建的树，尽管不太正确

 HuffmanNode rootTest=new HuffmanNode((byte)preOrderString.charAt(0));
    Stack<HuffmanNode> s = new Stack<HuffmanNode>(); 
    HuffmanNode current=rootTest;
    root=current;
    s.push(current);
    for(int i=1;i<preOrderString.length();i++) {
        if(preOrderString.charAt(i)=='0') {
            HuffmanNode next=new HuffmanNode((byte)preOrderString.charAt(i));
            if(current.left==null) 
                current.left=next;
            else
                current.right=next;
            current=next;
            System.out.println(current);
            s.push(current);
        }
        if(preOrderString.charAt(i)=='1') {
            i++;
            if(current.left==null) {
                current.left=new HuffmanNode((byte)preOrderString.charAt(i));
                System.out.println("left "+current.left);
            }
            else if(current.right==null){
                current.right=new HuffmanNode((byte)preOrderString.charAt(i));
                System.out.println("right "+current.right);
            }
            while(!s.isEmpty()) {
                current=s.pop();
            }
        }   
    }