c语言代码实现二叉树的以下功能。二叉树的创建、二叉树的三种递归遍历 二叉树的复制、统汁二叉树的结点数

以下是C语言代码实现二叉树的相关功能：

1. 二叉树的创建

#include <stdio.h>
#include <stdlib.h>

typedef struct TreeNode {
    int val;
    struct TreeNode *left;
    struct TreeNode *right;
} TreeNode;

TreeNode* createTree() {
    int val;
    scanf("%d", &val);
    if (val == -1) {
        return NULL;
    }
    TreeNode *root = (TreeNode*)malloc(sizeof(TreeNode));
    root->val = val;
    root->left = createTree();
    root->right = createTree();
    return root;
}

2. 二叉树的三种递归遍历

void preorder(TreeNode *root) {
    if (root == NULL) {
        return;
    }
    printf("%d ", root->val);
    preorder(root->left);
    preorder(root->right);
}

void inorder(TreeNode *root) {
    if (root == NULL) {
        return;
    }
    inorder(root->left);
    printf("%d ", root->val);
    inorder(root->right);
}

void postorder(TreeNode *root) {
    if (root == NULL) {
        return;
    }
    postorder(root->left);
    postorder(root->right);
    printf("%d ", root->val);
}

3. 二叉树的复制

TreeNode* copyTree(TreeNode *root) {
    if (root == NULL) {
        return NULL;
    }
    TreeNode *newRoot = (TreeNode*)malloc(sizeof(TreeNode));
    newRoot->val = root->val;
    newRoot->left = copyTree(root->left);
    newRoot->right = copyTree(root->right);
    return newRoot;
}

4. 统计二叉树的结点数

int countNodes(TreeNode *root) {
    if (root == NULL) {
        return 0;
    }
    return 1 + countNodes(root->left) + countNodes(root->right);
}