DS二叉树--后序遍历非递归算法

#include<iostream>
#include<stack>
using namespace std;
class CNode
{
public:
    char data;
    CNode *left;
    CNode *right;
    CNode()
    {
        left=right=NULL;
    }
};
 
class BiTree
{
public:
    CNode *Root;
    int pos;
    string strTree;
    BiTree(string str)
    {
        pos=0;
        strTree=str;
        Root=CreateBiTree();
    }
    CNode *CreateBiTree()
    {
        CNode *T;
        char ch;
        ch=strTree[pos];
        pos++;
        if(ch==‘0‘)
        {
            T=NULL;
        }
        else
        {
            T=new CNode();
            T->data=ch;
            T->left=CreateBiTree();
            T->right=CreateBiTree();
        }
        return T;
    }
    void nonPre()
    {
        CNode *T=Root;
        stack<CNode*>S;
        while(T||!S.empty())
        {
            while(T)
            {
                cout<<T->data;
                S.push(T);
                T=T->left;
            }
            if(!S.empty())
            {
                T=S.top();
                S.pop();
                T=T->right;
            }
        }
    }
    void nonPost()
    {
        int tag;///0不可访问，1可访问
        stack<CNode*>S1;///结点
        stack<int>S2;///tag
        CNode *T=Root;
        if(Root==NULL)
            return;
        CNode *p=T;
        do
        {
            while(p!=NULL)
            {
                S1.push(p);
                S2.push(0);
                p=p->left;
            }
            if(S1.empty())
                break;
            if(p==NULL)
            {
                tag=S2.top();
                if(tag==0)
                {
                    tag=1;
                    S2.pop();
                    S2.push(tag);
                    p=S1.top()->right;
                }
                else if(tag==1)
                {
                    p=S1.top();
                    S1.pop();
                    S2.pop();
                    cout<<p->data;
                    p=NULL;
                }
            }
        }while(!S1.empty());
    }
};
 
int main()
{
    int T;
    cin>>T;
    while(T--)
    {
        string str;
        cin>>str;
        BiTree tree(str);
        tree.nonPost();
        cout<<endl;
    }
    return 0;
}