Binary tree traversal non-recursion

Original http://www.wangchao.net.cn/bbsdetail_66513.html

 

1. Traverse non-Recursive Algorithms in sequence
# Define Max size 100
Typedef struct
{
Bitree Elem [maxsize];
Int top;
} SqStack;
Void PreOrderUnrec (Bitree t)
{
SqStack s;
StackInit (s );
P = t;
　　
While (p! = Null |! StackEmpty (s ))
{
While (p! = Null) // traverse the left subtree
{
Visite (p-> data );
Push (s, p );
P = p-> lchild;
} // Endwhile
　　
If (! StackEmpty (s) // uses the embedded while in the next loop to implement the right subtree Traversal
{
P = pop (s );
P = p-> rchild;
} // Endif
　　
} // Endwhile
　　
} // PreOrderUnrec
2. Non-recursive algorithm for sequential Traversal
# Define Max size 100
Typedef struct
{
Bitree Elem [maxsize];
Int top;
} SqStack;
Void InOrderUnrec (Bitree t)
{
SqStack s;
StackInit (s );
P = t;
While (p! = Null |! StackEmpty (s ))
{
While (p! = Null) // traverse the left subtree
{
Push (s, p );
P = p-> lchild;
} // Endwhile
　　
If (! StackEmpty (s ))
{
P = pop (s );
Visite (p-> data); // access the root node
P = p-> rchild; // use the next loop to traverse the right subtree
} // Endif
　　
} // Endwhile
} // InOrderUnrec
3. Post-order traversal of non-Recursive Algorithms
# Define Max size 100
Typedef enum {L, R} tagtype;
Typedef struct
{
Bitree ptr;
Tagtype tag;
} Stacknode;
Typedef struct
{
Stacknode Elem [maxsize];
Int top;
} SqStack;
Void PostOrderUnrec (Bitree t)
{
SqStack s;
Stacknode x;
StackInit (s );
P = t;
　　
Do
{
While (p! = Null) // traverse the left subtree
{
X. ptr = p;
X. tag = L; // mark as left subtree
Push (s, x );
P = p-> lchild;
}
　　
While (! StackEmpty (s) & s. Elem [s. top]. tag = R)
{
X = pop (s );
P = x. ptr;
Visite (p-> data); // The tag is R, indicating that the access to the right subtree is complete, so the access to the root node
}
　　
If (! Stackempty (s ))
{
S. ELEM [S. Top]. Tag = r; // traverse the right subtree
P = S. ELEM [S. Top]. PTR-> rchild;
}
} While (! Stackempty (s ));
} // Postorderunrec