二叉树链式结构的实现

对于二叉树链式结构的实现，理解二叉树的概念至关重要。在二叉树的创建以及求二叉树叶子节点的个数等其他操作时，都是先从二叉树的概念入手，一步一步完成二叉树的创建及其他操作，接下来看一下二叉树的概念

• 二叉树的概念
  • 空树
  • 根节点+根节点的左子树+根节点的右子树
• 接下来是二叉树的具体实现
  BinaryTree.h实现

#pragma once
typedef char DataType;
typedef struct BNode{
struct BNode* left;
struct BNode* right;
DataType data;
}BNode;
BNode* BuyBinTreeNode(DataType data);
BNode* CreateBinTree(DataType* array, int size,DataType invalid);
BNode* _CreateBinTree(DataType* array, int size, int* index, int invalid);
void LevelOrder(BNode* root);
BNode* Find(BNode* root, DataType data);
int GetKLevelNodeCount(BNode* root, int K);
int GetLeafCount(BNode* root);
void PreOrder(BNode* root);
void DestroyBinTree(BNode** root);
void TestBinTree();

BinaryTree.c实现

#include"BinaryTree.h"
#include
#include
#include
#include
BNode* BuyBinTreeNode(DataType data) {
 BNode* pNewNode = (BNode*)malloc(sizeof(BNode));
 if (pNewNode == NULL) {
  assert(0);
  return NULL;
 }
 pNewNode->left = NULL;
 pNewNode->right = NULL;
 pNewNode->data = data;
 return pNewNode;
}
BNode* CreateBinTree(DataType* array, int size,DataType invalid) {
 int index = 0;
 return _CreateBinTree(array, size, &index,invalid);
}
BNode* _CreateBinTree(DataType* array, int size,int* index,int invalid) {
 //用树的概念
 //根节点
 BNode* pRoot = NULL;
 if (*index < size&&'$'!=array[*index]) {
  pRoot = BuyBinTreeNode(array[*index]);
  ++(*index);
  //根的左子树
  pRoot->left = _CreateBinTree(array, size, index, invalid);
  //根的右子树
  ++(*index);
  pRoot->right = _CreateBinTree(array, size, index, invalid);
 }
 return pRoot;
}
int GetKLevelNodeCount(BNode* root, int K) {
 if (root == NULL || K <= 0) {
  return 0;
 }
 if (K == 1) {
  return 1;
 }
 return GetKLevelNodeCount(root->left, K - 1) + GetKLevelNodeCount(root->right, K - 1);
}
int GetLeafCount(BNode* root) {
 if (root == NULL) {
  return 0;
 } else if (root->left == NULL && root->right == NULL) {
  return 1;
 }
 return GetLeafCount(root->left) + GetLeafCount(root->right);
}
void PreOrder(BNode* root) {
 if (root) {
  printf("%c ", root->data);
  PreOrder(root->left);
  PreOrder(root->right);
 }
}
void InOrder(BNode* root) {
 if (root) {
  InOrder(root->left);
  printf("%c ", root->data);
  InOrder(root->right);
 }
}
void PostOrder(BNode* root) {
 if (root) {
  PostOrder(root->left);
  PostOrder(root->right);
  printf("%c ", root->data);
 }
}
BNode* Find(BNode* root, DataType data) {
 if (root == NULL) {
  return NULL;
 } else if (root->data == data) {
  return root;
 }
 BNode* pNode = NULL;
 if (pNode = Find(root->left, data)) {
  return pNode;
 }
 return Find(root->right, data);
}
void DestroyBinTree(BNode** root) {
 assert(root);
 if (*root) {
  DestroyBinTree(&(*root)->left);
  DestroyBinTree(&(*root)->right);
  free(*root);
  *root = NULL;
 }
}
void TestBinTree() {
 char* str = "ABD$$$CE$$F";
 BNode* pRoot = CreateBinTree(str,strlen(str),'$');
 printf("前序遍历结果为:");
 PreOrder(pRoot);
 printf("\n");
 printf("中序遍历结果为:");
 InOrder(pRoot);
 printf("\n");
 printf("后序遍历结果为:");
 PostOrder(pRoot);
 printf("\n");
 printf("K=3: %d\n", GetKLevelNodeCount(pRoot, 3));
 if (Find(pRoot, 'E')) {
  printf("找到了!!!\n");
 } else {
  printf("没找到!!!\n");
 }
 DestroyBinTree(&pRoot);
}