请各位变成高手给查查错

#include <iostream>
using namespace std;
struct t
{
    char e;
    t *lc,*rc;
};
int whil=1;
void ct(t *root)
{
    char ee;
    cin>>ee;
    if(ee=='.') root=NULL;
    else
    {
        root=new t;
        root->e=ee;
        ct(root->lc);
        ct(root->rc);
    }
}
void dlr(t *root)
{
    if(root!=NULL)
    {
        cout<<root->e;
        dlr(root->lc);
        dlr(root->rc);
    }
    cout<<endl<<"先序遍历完成"<<endl;
}
void ldr(t *root)
{
    if(root!=NULL)
    {
        ldr(root->lc);
        cout<<root->e;
        ldr(root->rc);
    }
    cout<<endl<<"中序遍历完成"<<endl;
}
void lrd(t *root)
{
    if(root!=NULL)
    {
        lrd(root->lc);
        lrd(root->rc);
        cout<<root->e;
    }
    cout<<endl<<"后序遍历完成"<<endl;
}
void vt(t *root)
{
    if(root!=NULL)
    {
        if(root->rc==NULL&&root->rc==NULL) cout<<root->e;
        dlr(root->lc);
        dlr(root->rc);
    }
    cout<<endl<<"叶子节点输出完成"<<endl;
}                                                
int main()
{
    t tree;
    while(whil)
    {
        char a;
        cout<<"请选择操作：1 创建树 2 遍历树 3 叶子结点输出 4 结束程序"<<endl;
        cin>>a;
        switch(a)
        {
        case '1':ct(&tree);break;
        case '2':
            {
                dlr(&tree);
                ldr(&tree);
                lrd(&tree);
            };break;
        case '3':ct(&tree);break;
        case '4':whil=0;break;
        default:cout<<"无此选项"<<endl;
        }
        system("pause");
        system("cls");
    }
    return 0;
}
这段关于二叉树的代码，为什么无法遍历