為什么即使我在另一個節點中復制了根節點，我的原始二叉搜索樹也會被修改？

Question

我的老師給了我們一個作業來編寫二進制搜索樹。 大部分已經完成，但是我在處理二叉樹的鏡像時遇到了問題。 老師告訴我們，我們應該在不改變原始樹的情況下創建一個鏡像。 我嘗試創建它，但代碼也會修改原始 BST，如下面的輸出所示。 我不明白哪里出了問題。 任何幫助，將不勝感激。

我的代碼：

#include<iostream>
using namespace std;
struct node
{
    int data;
        node *left,*right;
};
class BST
{
    node *root,*root1;
    public:
        int ch;
    BST(){   root=NULL;     ch=0;    }    
        void create();
    void insert(node*,node*);
    void disin();   
    void inorder(node*);
    void dispre();  
    void preorder(node*);
    void dispost(); 
    void postporder(node*);
    void search();
    node* actualsearch(node*,int);
    void min();
    void max();
    void actmin(node*);
    void actmax(node*);
    void height();
    int actheight(node*);
    void mirror();
    void actmirror(node*);
};
int main()
{
    int cho;
    BST b;
    char choice;
    do  {
    cout<<"\nEnter Your Choice = ";
    cout<<"\n1.Insert";
    cout<<"\n2.Inorder Traversal";
    cout<<"\n3.Preorder Traversal";
    cout<<"\n4.Postorder Traversal";
    cout<<"\n5.Search an element in tree";
    cout<<"\n6.Find Maximum element in tree";
    cout<<"\n7.Find Minimum elemnt in tree";
    cout<<"\n8.Total No Of Nodes In Longest Path";
    cout<<"\n9.Mirror Image = ";
    cin>>cho;
    switch(cho)
    {
        case 1:
            b.create();
            break;

        case 2:
            cout<<"---------------------------------------------------";
            cout<<"\nInorder Treaversal = "<<endl;
            b.disin();
            cout<<"\n---------------------------------------------------";      
            break;

        case 3:
            cout<<"---------------------------------------------------";
            cout<<"\nPreorder Treaversal = "<<endl;
            b.dispre();
            cout<<"\n---------------------------------------------------";      
            break;

        case 4:
            cout<<"---------------------------------------------------";
            cout<<"\nPostorder Treaversal = "<<endl;
            b.dispost();
            cout<<"\n---------------------------------------------------";      
            break;  

        case 5:
            b.search();
            cout<<"\n---------------------------------------------------";
            break;
        case 6:
            b.max();
            cout<<"\n---------------------------------------------------";
            break;
        case 7:
            b.min();
            cout<<"\n---------------------------------------------------";
            break;
        case 8:
            b.height();
            cout<<"\n---------------------------------------------------";
            break;
        case 9:
            b.mirror();
            cout<<"\n---------------------------------------------------";
            break;

    }
    cout<<"\nDo you want to continue opreations(y/n) = ";
    cin>>choice;    
    }while(choice=='y'||choice=='Y');
    return 0;
}

void BST::search()
{
    int n;
    cout<<"\nEnter element you want to search = ";
    cin>>n;
    if(root!=NULL)
        actualsearch(root,n);
    else
        cout<<"Tree is empty"<<endl;        
}
node* BST::actualsearch(node *current,int n)
{
    int dfcount=0;
    while(current)
    {
        if(current->data==n)
        {
            cout<<"Data Found"<<endl;
            dfcount++;
            break;
        }
        else if(n>current->data)
            {
                current=current->right;
            }
        else if(n<current->data)
            {
                current=current->left;
            }
    }
    if(dfcount==0)
    cout<<"Data not found!"<<endl;
    return NULL;
}

void BST::create()
{
    char ans;
    node *temp;
    do
    {
        temp=new node;
        temp->left=temp->right=NULL;
        cout<<"\nEnter no you want to insert = ";
        cin>>temp->data;
        if(root==NULL)
        {
            root=temp;
        }
        else
        {
            insert(root,temp);
        }
        cout<<"\nDo You want to continue to insert data(y/n) = ";
        cin>>ans;
    }while(ans=='y'||ans=='Y');
}

void BST::insert(node *current,node *temp)
{
    if(temp->data==current->data)
        cout<<"\nDo not add";

    else if(temp->data<current->data)
    {
        if(current->left==NULL)
            current->left=temp;
        else
            insert(current->left,temp);
    }
    else if(temp->data>current->data)
    {
        if(current->right==NULL)
            current->right=temp;
        else
            insert(current->right,temp);
    }                   
}

void BST::disin()
{

    inorder(root);
}

void BST::inorder(node *T)
{   

    if(T!=NULL)
     {
        inorder(T->left);
        cout<<T->data<<" "; 
        inorder(T->right);
    }
}


void BST::dispre()
{

    preorder(root);
}

void BST::preorder(node *T)
{   

    if(T!=NULL)
     {
        cout<<T->data<<" "; 
        preorder(T->left);
        preorder(T->right);
    }
}


void BST::dispost()
{

    postporder(root);
}

void BST::postporder(node *T)
{   

    if(T!=NULL)
     {
        postporder(T->left);    
        postporder(T->right);
        cout<<T->data<<" "; 
    }
}
void BST::max()
{
    if(root!=NULL)
    {
        actmax(root);
    }
}
void BST::min()
{
    if(root!=NULL)
    {
        actmin(root);
    }
}
void BST::actmax(node* current)
{
    while(current->right!=NULL)
    {
        current=current->right;
    }
    cout<<"Largest Number is :"<<current->data<<endl;
}
void BST::actmin(node* current)
{
    while(current->left!=NULL)
    {
        current=current->left;
    }
    cout<<"Smallest Number is :"<<current->data<<endl;
}
void BST::height()
{
    int i=actheight(root);
    cout<<"Total No Of Nodes In Longest Path is:"<<i<<endl;
}
int BST::actheight(node* current)
{
    if(current==NULL)
    {
        return 0;
    }
    else
    {
        int lh = actheight(current->left);
        int rh = actheight(current->right);
        if (lh > rh)  
           return(lh+1);
        else return(rh+1);
    }

}
void BST::mirror()
{   root1=root;
    actmirror(root1);
    cout<<"Mirror Image of given tree is Created!"<<endl;
    cout<<"\nInorder Travesral Is = "<<endl;
    inorder(root1);
    cout<<"\nPreorder Travesral Is = "<<endl;
    preorder(root1);
    cout<<"\nPostorder Travesral Is = "<<endl;
    postporder(root1);

}
void BST::actmirror(node* current)
{
    node* holder=new node;
    if(current==NULL)
    {
        return ;    
    }

    holder=current->left;
    current->left=current->right;
    current->right=holder;
    actmirror(current->left);
    actmirror(current->right);
}

它的輸出：

Enter Your Choice =
1.Insert
2.Inorder Traversal
3.Preorder Traversal
4.Postorder Traversal
5.Search an element in tree
6.Find Maximum element in tree
7.Find Minimum elemnt in tree
8.Total No Of Nodes In Longest Path
9.Mirror Image = 1

Enter no you want to insert = 5

Do You want to continue to insert data(y/n) = y

Enter no you want to insert = 6

Do You want to continue to insert data(y/n) = y

Enter no you want to insert = 7

Do You want to continue to insert data(y/n) = y

Enter no you want to insert = 2

Do You want to continue to insert data(y/n) = y

Enter no you want to insert = 3

Do You want to continue to insert data(y/n) = n

Do you want to continue opreations(y/n) = y

Enter Your Choice =
1.Insert
2.Inorder Traversal
3.Preorder Traversal
4.Postorder Traversal
5.Search an element in tree
6.Find Maximum element in tree
7.Find Minimum elemnt in tree
8.Total No Of Nodes In Longest Path
9.Mirror Image = 2
---------------------------------------------------
Inorder Treaversal =
2 3 5 6 7
---------------------------------------------------
Do you want to continue opreations(y/n) = y

Enter Your Choice =
1.Insert
2.Inorder Traversal
3.Preorder Traversal
4.Postorder Traversal
5.Search an element in tree
6.Find Maximum element in tree
7.Find Minimum elemnt in tree
8.Total No Of Nodes In Longest Path
9.Mirror Image = 9
Mirror Image of given tree is Created!

Inorder Travesral Is =
7 6 5 3 2
Preorder Travesral Is =
5 6 7 2 3
Postorder Travesral Is =
7 6 3 2 5
---------------------------------------------------
Do you want to continue opreations(y/n) = y

Enter Your Choice =
1.Insert
2.Inorder Traversal
3.Preorder Traversal
4.Postorder Traversal
5.Search an element in tree
6.Find Maximum element in tree
7.Find Minimum elemnt in tree
8.Total No Of Nodes In Longest Path
9.Mirror Image = 2
---------------------------------------------------
Inorder Treaversal =
7 6 5 3 2
---------------------------------------------------
Do you want to continue opreations(y/n) = n

--------------------------------
Process exited after 41 seconds with return value 0
Press any key to continue . . .

在這里你可以看到，即使我使用了普通的中序遍歷，它也沒有顯示原始 BST 的遍歷，而是顯示了鏡像 BST 的遍歷。

Answer 1

Traversal 它不顯示原始 BST 的遍歷，而是顯示鏡像 BST 的遍歷。

在

void BST::actmirror(node* current) { node* holder=new node; if(current==NULL) { return ; } holder=current->left; current->left=current->right; current->right=holder; actmirror(current->left); actmirror(current->right); }

由於holder=current->left;分配的新節點丟失holder=current->left; 並且您像 drescherjm 在評論中所說的那樣修改當前節點而不是新節點

---

一個建議：在BST類中，將BST::actmirror的簽名更改為node* BST::actmirror(node* current) ，並將其定義更改為：

node*  BST::actmirror(node* current)
{
    if(current==NULL)
    {
        return 0;    
    }

    node* holder=new node;

    holder->data = current->data;
    holder->left = actmirror(current->right);
    holder->right = actmirror(current->left);
    return holder;
}

正如你所看到的，同時創建的鏡像是一個副本

並像這樣更新BST::mirror() ：

void BST::mirror()
{   node * copy1 = actmirror(root);
    cout<<"Mirror Image of given tree is Created!"<<endl;
    cout<<"\nInorder Travesral Is = "<<endl;
    inorder(copy1);
    cout<<"\nPreorder Travesral Is = "<<endl;
    preorder(copy1);
    cout<<"\nPostorder Travesral Is = "<<endl;
    postporder(copy1);

    // WARNING here you need to delete the copy !
}

正如我在評論中所說，如果鏡像同時制作副本和鏡像會更好，我上面是這樣做的。

現在執行是：

Enter Your Choice = 
1.Insert
2.Inorder Traversal
3.Preorder Traversal
4.Postorder Traversal
5.Search an element in tree
6.Find Maximum element in tree
7.Find Minimum elemnt in tree
8.Total No Of Nodes In Longest Path
9.Mirror Image = 1

Enter no you want to insert = 5

Do You want to continue to insert data(y/n) = y

Enter no you want to insert = 6

Do You want to continue to insert data(y/n) = y

Enter no you want to insert = 7

Do You want to continue to insert data(y/n) = y

Enter no you want to insert = 2

Do You want to continue to insert data(y/n) = y

Enter no you want to insert = 3

Do You want to continue to insert data(y/n) = n

Do you want to continue opreations(y/n) = y

Enter Your Choice = 
1.Insert
2.Inorder Traversal
3.Preorder Traversal
4.Postorder Traversal
5.Search an element in tree
6.Find Maximum element in tree
7.Find Minimum elemnt in tree
8.Total No Of Nodes In Longest Path
9.Mirror Image = 2
---------------------------------------------------
Inorder Treaversal = 
2 3 5 6 7 
---------------------------------------------------
Do you want to continue opreations(y/n) = y

Enter Your Choice = 
1.Insert
2.Inorder Traversal
3.Preorder Traversal
4.Postorder Traversal
5.Search an element in tree
6.Find Maximum element in tree
7.Find Minimum elemnt in tree
8.Total No Of Nodes In Longest Path
9.Mirror Image = 9
Mirror Image of given tree is Created!

Inorder Travesral Is = 
7 6 5 3 2 
Preorder Travesral Is = 
5 6 7 2 3 
Postorder Travesral Is = 
7 6 3 2 5 
---------------------------------------------------
Do you want to continue opreations(y/n) = y

Enter Your Choice = 
1.Insert
2.Inorder Traversal
3.Preorder Traversal
4.Postorder Traversal
5.Search an element in tree
6.Find Maximum element in tree
7.Find Minimum elemnt in tree
8.Total No Of Nodes In Longest Path
9.Mirror Image = 2
---------------------------------------------------
Inorder Treaversal = 
2 3 5 6 7 
---------------------------------------------------
Do you want to continue opreations(y/n) = n