Layered traversal of Binary Trees

Problem:

How can we achieve layered traversal of Binary Trees?

Resolution:

We can use the queue to solve this problem.

<1> press the root node into the queue.

<2> check whether the queue is empty.

<3> if this parameter is not set, the frontend element of the queue is obtained and printed.

<4> remove this element from the queue

<5> If the element has a left child, the left child enters the queue.

<6> If the element has a right child, the Right child enters the queue.

The main functions are as follows:

template<typename Type> void BSTrees<Type>::traverseLevel(Node* root){if( root == NULL){cout<<"This is a empty tree"<<endl;return;}queue<Node*> que;que.push(root);while( !que.empty() ){Node* ptr = que.front();que.pop();cout<<ptr->e<<endl;if(ptr->leftChild != NULL)que.push(ptr->leftChild);if(ptr->rightChild != NULL)que.push(ptr->rightChild);}}

All programs are as follows:

//BSTrees.h#ifndef DDXX_BSTREES_H#define DDXX_BSTREES_H#include <iostream>#include <queue>using namespace std;template<typename Type>class BSTrees{public:BSTrees();~BSTrees();public:struct Node{Typee;Node*leftChild;Node*rightChild;Node(){}Node(Type _e){e= _e;leftChild= NULL;rightChild= NULL;}};public:boolinsert(Type e);boolerase1(Type e);boolerase2(Type e);voidclear();boolisEmpty();intgetLength();Node*find(Type e);Node*getRoot();Node*getParent(Node* p);voidtraverse(Node* ptr);voidtraverseLevel(Node* ptr);private:voidclears(Node* &p);private:Node*m_root;intm_Length;};template<typename Type> BSTrees<Type>::BSTrees(){m_root = NULL;m_Length = 0;}template<typename Type> bool BSTrees<Type>::insert(Type e){Node* ptr = new Node(e);if ( ptr == NULL ){cout<<"Allocate memory for the element failed"<<endl;return false;}if( m_root == NULL){m_root = ptr;m_Length++;return true;}Node* p= m_root;Node* pParent= m_root;while( p != NULL){if( e == p->e){cout<<"the element is already exist"<<endl;delete ptr;ptr = NULL;return false;}pParent = p;if( e > p->e){p = p->rightChild;}else{p = p->leftChild;}}if( e < pParent->e ){pParent->leftChild = ptr;}if( e > pParent->e){pParent->rightChild = ptr;}m_Length++;return true;}template<typename Type> bool BSTrees<Type>::erase1(Type e){Node *p = find(e);if ( p == NULL ){cout<<"There's no this element to delete"<<endl;return false;}if ( p->leftChild == NULL){Node* pParent = getParent(p);if( pParent->leftChild == p )pParent->leftChild = p->rightChild;elsepParent->rightChild = p->rightChild;delete p;p = NULL;m_Length--;return true;}if ( p->rightChild == NULL){Node* pParent = getParent(p);if( pParent->leftChild == p)pParent->leftChild = p->leftChild;elsepParent->rightChild = p->leftChild;delete p;p = NULL;m_Length--;return true;}if ( p->leftChild != NULL && p->rightChild != NULL){Node* pParent = getParent(p);Node* pPre = p->leftChild;Node* ptmp = pPre;while( pPre->rightChild != NULL ){ptmp = pPre;pPre = pPre->rightChild;}if( ptmp != pPre){ptmp->rightChild = pPre->leftChild;pPre->leftChild = p->leftChild;pPre->rightChild = p->rightChild;}elsepPre->rightChild = p->rightChild;if( pParent == NULL )m_root = pPre;else if( pParent->leftChild == p)  pParent->leftChild = pPre;elsepParent->rightChild = pPre;delete p;p = NULL;m_Length--;return true;}}template<typename Type> boolBSTrees<Type>::erase2(Type e){Node *p = find(e);if ( p == NULL ){cout<<"There's no this element to delete"<<endl;return false;}if ( p->leftChild == NULL){Node* pParent = getParent(p);if( pParent->leftChild == p )pParent->leftChild = p->rightChild;elsepParent->rightChild = p->rightChild;delete p;p = NULL;m_Length--;return true;}if ( p->rightChild == NULL){Node* pParent = getParent(p);if( pParent->leftChild == p)pParent->leftChild = p->leftChild;elsepParent->rightChild = p->leftChild;delete p;p = NULL;m_Length--;return true;}if( p->leftChild != NULL && p->rightChild != NULL){Node* pParent = getParent(p);Node* ptr = p->leftChild;while( ptr->rightChild != NULL )ptr = ptr->rightChild;ptr->rightChild = p->rightChild;if( pParent == NULL )m_root = p->leftChild;elseif(pParent->leftChild == p)pParent->leftChild = p->leftChild;elsepParent->rightChild = p->leftChild;delete p;p = NULL;m_Length--;return true;}}template<typename Type> voidBSTrees<Type>::clear(){if( m_root == NULL )return;clears(m_root);m_root = NULL;}template<typename Type> void BSTrees<Type>::clears(Node* &p){if(p->leftChild != NULL){clears(p->leftChild);p->leftChild = NULL;}if(p->rightChild != NULL){clears(p->rightChild);p->rightChild = NULL;}delete p;p = NULL;m_Length--;}template<typename Type> typename BSTrees<Type>::Node* BSTrees<Type>::getRoot(){return m_root;}template<typename Type> intBSTrees<Type>::getLength(){return m_Length;}template<typename Type> typename BSTrees<Type>::Node* BSTrees<Type>::getParent(Node* p){if( p == m_root)return NULL;Node* ptr = m_root;Node* ptf = ptr;while( ptr != NULL ){if ( ptr->e == p->e )return ptf;if ( ptr->e > p->e ){ptf = ptr;ptr = ptr->leftChild;}else{ptf = ptr;ptr = ptr->rightChild;}}}template<typename Type> typename BSTrees<Type>::Node* BSTrees<Type>::find(Type e){Node* ptr = m_root;while(ptr != NULL){if ( ptr->e == e )return ptr;if ( ptr->e > e )ptr = ptr->leftChild;elseptr = ptr->rightChild;}//if ( ptr == NULL )return NULL;}template<typename Type> void BSTrees<Type>::traverse(Node* ptr){if( ptr == NULL )return;if( ptr->leftChild != NULL )traverse(ptr->leftChild);cout<<"Element value:"<<ptr->e<<endl;if( ptr->rightChild != NULL )traverse(ptr->rightChild);}template<typename Type> void BSTrees<Type>::traverseLevel(Node* root){if( root == NULL){cout<<"This is a empty tree"<<endl;return;}queue<Node*> que;que.push(root);while( !que.empty() ){Node* ptr = que.front();que.pop();cout<<ptr->e<<endl;if(ptr->leftChild != NULL)que.push(ptr->leftChild);if(ptr->rightChild != NULL)que.push(ptr->rightChild);}}template<typename Type> BSTrees<Type>::~BSTrees(){clear();}#endif

#include <iostream>#include "BST.h"using namespace std;void main(){BSTrees<int>Bst;      int Arr[9] = {6,2,8,4,10,0,12,16,14};      for (int i=0;i<9;i++)              Bst.insert(Arr[i]);      Bst.traverse(Bst.getRoot());      cout<<"Tree'slength is:"<<Bst.getLength()<<endl; Bst.traverseLevel(Bst.getRoot());}

Layered traversal of Binary Trees