举例讲解C语言程序中对二叉树数据结构的各种遍历方式

#include <stdio.h> 
#include <stdlib.h> 
 
typedef struct _NODE//节点结构 
{ 
  struct _NODE* leftChild; 
  int value; 
  struct _NODE* rightChild; 
} NODE, *PNODE; 
 
PNODE createNode(int value){//创建一个新节点 
  PNODE n = (PNODE)malloc(sizeof(NODE)); 
  n->value = value; 
  n->leftChild = NULL; 
  n->rightChild = NULL; 
  return n; 
} 
 
PNODE insertLeftChild(PNODE parent, int value){//在指定节点上插入左节点 
  return (parent->leftChild = createNode(value)); 
} 
 
PNODE insertRightChild(PNODE parent, int value){//在指定节点上插入左节点 
  return (parent->rightChild = createNode(value)); 
} 
 
void createBTree(PNODE root, int i){//向树中插入一些元素    
  if (i == 0)                              
  {                             
    return;                         
  }                             
  else{ 
    PNODE l = insertLeftChild(root, i * 10 + 1); 
    PNODE r = insertRightChild(root, i * 10 + 2); 
    createBTree(l, --i); 
    createBTree(r, i); 
  } 
} 
 
void printDLR(PNODE root){//先序遍历：对每一刻子树都是根->左->右的顺序 
  if (root == NULL) 
  { 
    return; 
  } 
  printf("%-4d", root->value); 
  printDLR(root->leftChild); 
  printDLR(root->rightChild); 
} 
 
void printLDR(PNODE root){//中序遍历： 
  if (root == NULL) 
  { 
    return; 
  } 
  printLDR(root->leftChild); 
  printf("%-4d", root->value); 
  printLDR(root->rightChild); 
} 
 
void printLRD(PNODE root){//后序遍历 
  if (root == NULL) 
  { 
    return; 
  } 
  printLRD(root->leftChild); 
  printLRD(root->rightChild); 
  printf("%-4d", root->value); 
} 
 
void main(){ 
  PNODE root = createNode(0);//创建根节点 
  createBTree(root, 3); 
   
  printf("先序遍历: "); 
  printDLR(root);//遍历 
  printf("\n中序遍历: "); 
   
  printLDR(root); 
  printf("\n后序遍历: "); 
   
  printLRD(root); 
  printf("\n"); 
} 

#include <iostream.h> 
 
template <class T> class Node//节点类模板 
{ 
public: 
  Node(T value):value(value)//构造方法 
  { 
    leftChild = 0;  
    rightChild = 0; 
  } 
  Node* insertLeftChild(T value);//插入左孩子,返回新节点指针 
  Node* insertRightChild(T vallue);//插入右孩子 
  void deleteLeftChild();//删左孩子 
  void deleteRightChild();//删右孩子 
  void showDLR();//先序遍历 
  void showLDR();//中序遍历 
  void showLRD();//后序遍历 
protected: 
  T value;//节点值 
  Node* leftChild;//左孩子指针 
  Node* rightChild;//右孩子指针 
private: 
}; 
 
template <class T> Node<T>* Node<T>::insertLeftChild(T value){//插入左孩子 
  return (this->leftChild = new Node(value)); 
} 
 
template <class T> Node<T>* Node<T>::insertRightChild(T value){//插入右孩子 
  return (this->rightChild = new Node(value)); 
} 
 
template <class T> void Node<T>::deleteLeftChild(){//删除左孩子 
  delete this->leftChild; 
  this->leftChild = 0; 
} 
 
template <class T> void Node<T>::deleteRightChild(){//删除右孩子 
  delete this->rightChild; 
  this->rightChild = 0; 
} 
 
template <class T> void Node<T>::showDLR(){//先序遍历 
  cout<<this->value<<" "; 
  if (leftChild) 
  { 
    leftChild->showDLR(); 
  } 
  if (rightChild) 
  { 
    rightChild->showDLR(); 
  } 
} 
 
template <class T> void Node<T>::showLDR(){//中序遍历 
  if (leftChild) 
  { 
    leftChild->showLDR(); 
  } 
  cout<<this->value<<" "; 
  if (rightChild) 
  { 
    rightChild->showLDR(); 
  } 
} 
 
template <class T> void Node<T>::showLRD(){//后序遍历 
  if (leftChild) 
  { 
    leftChild->showLRD(); 
  } 
  if (rightChild) 
  { 
    rightChild->showLRD(); 
  } 
  cout<<this->value<<" "; 
} 
 
template <class T> void createSomeNodes(Node<T>* root, int i, T base){//构建一个二叉树 
  if (i == 0) 
  { 
    return; 
  } 
  Node<T>* l = root->insertLeftChild(i + base); 
  Node<T>* r = root->insertRightChild(i + base); 
  createSomeNodes(l, --i, base); 
  createSomeNodes(r, i, base); 
} 
 
template <class T> void showTest(Node<T>* root){//显示各种遍历方式结果 
  cout<<"先序遍历: "; 
  root->showDLR(); 
  cout<<endl<<"中序遍历: "; 
  root->showLDR(); 
  cout<<endl<<"后序遍历: "; 
  root->showLRD(); 
  cout<<endl; 
} 
 
void main(){ 
  Node<int> *root1 = new Node<int>(0); 
  createSomeNodes(root1, 3, 0); 
  cout<<"整型:"<<endl; 
  showTest(root1); 
 
  Node<char> *root2 = new Node<char>('a'); 
  createSomeNodes(root2, 3, 'a'); 
  cout<<"字符型:"<<endl; 
  showTest(root2); 
 
  Node<float> *root3 = new Node<float>(0.1f); 
  createSomeNodes(root3, 3, 0.1f); 
  cout<<"浮点型:"<<endl; 
  showTest(root3); 
}