Python programming data structure and algorithm practice _009

Practice content:

Determine if a tree is a search binary tree.

Body Content Summary:

1. Create a class to implement a doubly linked list and basic stack structure.
2. Create a class to represent a binary tree.
3. Determine whether a tree is a recursive and non-recursive implementation of a search binary tree.
4. Simple test, verify correctness.

1. Create a class to implement a doubly linked list and basic stack structure. The code is as follows:

classdoublelinkedlist:classNode:def __init__(self, data): Self._data=Data Self._next=None Self._pre=Nonedef __init__(self): self.__head= Doublelinkedlist.node ("__head") self.__tail= Doublelinkedlist.node ("__tail") self.__head. _next = self.__tailSelf .__tail. _pre = self.__head    defAppend (self, data): node=Doublelinkedlist.node (data) self.__tail. _pre._next =node Node._pre= self.__tail. _pre self.__tail. _pre =node Node._next= self.__tail    defRemove (self, data): node= self.__head         whileNode! = self.__tail:            ifNode._data = =Data:node._pre._next=Node._next Node._next._pre=Node._pre Breaknode=Node._nextdefpop (self): node= self.__tail. _preifNode! = self.__head: Node._pre._next=Node._next Node._next._pre=Node._pre Node._next=None Node._pre=NonereturnNode._datareturnNonedefIs_empty (self)BOOL:returnSelf.__head. _next = = self.__tail    defIternodes (self)None:node= self.__head. _next whileNode! = self.__tail:            yieldnode._data Node=Node._nextdefAdd_last (self, data:object)None:self.append (data)defPoll_first (Self): node= self.__head. _nextifNode! = self.__tail: Self.__head. _next =Node._next Node._next._pre= self.__headNode._next=None Node._pre=NonereturnNode._datareturnNonedefPoll_last (self):returnSelf.pop ()defPeek_first (Self): node= self.__head. _nextifNode! = self.__tail:            returnNode._datareturnNonedefPeek_last (Self): node= self.__tail. _preifNode! = self.__head:            returnNode._datareturnNoneclassStack:def __init__(self): self.__dlnklst=doublelinkedlist ()defpop (self):returnSelf.__dlnklst. Pop ()defAdd (self, data): Self.__dlnklst. Append (data)defpush (self, data):returnSelf.__dlnklst. Append (data)defPeek (self):returnSelf.__dlnklst. Peek_last ()defpoll (self):returnSelf.__dlnklst. Poll_last ()defIs_empty (self):returnSelf.__dlnklst. Is_empty ()

2. Create a class to represent a binary tree. The code is as follows:

classNode:def __init__(self, data): Self.__data=data self.__left=None self.__right=None @propertydefdata (self):returnSelf.__data@propertydefLeft (self):returnSelf.__left@left. SetterdefLeft (Self, node): Self.__left=node @propertydefRight (self):returnSelf.__right@right. SetterdefRight (Self, node): Self.__right= Node

3. Determine whether a tree is a recursive and non-recursive implementation of a search binary tree. The code is as follows:

defIs_bst_recur (Head, pre=None):if  notHead:returnTrue cur=Headif  notis_bst_recur (Cur.left, pre):returnFalseifPre andPre.data >Cur.data:returnFalse Pre=curreturnis_bst_recur (cur.right, Pre)defIs_bst_unrecur (head):if  notHead:returnStack=Stack () Pre=None while  notStack.is_empty ()orHead:ifHead:stack.add (head) head=Head.leftElse: Head=Stack.pop ()ifPre andPre.data >Head.data:returnFalse Pre=Head Head=Head.rightElse:        returnTrue

4. Simple test, verify correctness. The code is as follows:

if __name__=="__main__":    #BSTHead1 = Node (9) Head1.left= Node (8) Head1.right= Node (10) Head1.left.left= Node (7) Head1.left.right= Node (9) Head1.right.left= Node (9) Head1.right.right= Node (11)    Print(Is_bst_recur (HEAD1))#True    Print(Is_bst_unrecur (HEAD1))#True    #Not BSTHead2 = Node (9) Head2.left= Node (8) Head2.right= Node (1) Head2.left.left= Node (7) Head2.left.right= Node (9) Head2.right.left= Node (9) Head2.right.right= Node (11)    Print(Is_bst_recur (HEAD2))#False    Print(Is_bst_unrecur (HEAD2))#False

Python programming data structure and algorithm practice _009