c语言用递归的方法实现以下算法: 1.以二叉链表表示二叉树,建立一棵二叉树(算法 5.3); 2.输出二叉树的中序遍历结果(算法 5.1); 3.输出二叉树的前序遍历结果(见讲稿); 4.输出二叉树的后序遍历结果(见讲稿) 并举一个输出案例

以下是用递归实现建立一棵二叉树的算法：

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

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

TreeNode *createTree() {
    int data;
    scanf("%d", &data);
    if (data == -1) {
        return NULL;
    }
    TreeNode *root = (TreeNode*)malloc(sizeof(TreeNode));
    root->data = data;
    printf("Enter left child of %d: \n", data);
    root->left = createTree();
    printf("Enter right child of %d: \n", data);
    root->right = createTree();
    return root;
}

以下是用递归实现中序遍历二叉树的算法：

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

以下是用递归实现前序遍历二叉树的算法：

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

以下是用递归实现后序遍历二叉树的算法：

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

下面是一个示例代码，建立了一棵二叉树并输出了它的中序遍历、前序遍历和后序遍历结果：

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

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

TreeNode *createTree() {
    int data;
    scanf("%d", &data);
    if (data == -1) {
        return NULL;
    }
    TreeNode *root = (TreeNode*)malloc(sizeof(TreeNode));
    root->data = data;
    printf("Enter left child of %d: \n", data);
    root->left = createTree();
    printf("Enter right child of %d: \n", data);
    root->right = createTree();
    return root;
}

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

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

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

int main() {
    printf("Enter the root node: ");
    TreeNode *root = createTree();

    printf("Inorder traversal: ");
    inorder(root);
    printf("\n");

    printf("Preorder traversal: ");
    preorder(root);
    printf("\n");

    printf("Postorder traversal: ");
    postorder(root);
    printf("\n");

    return 0;
}

示例输入为：

Enter the root node: 1
Enter left child of 1: 
2
Enter left child of 2: 
-1
Enter right child of 2: 
-1
Enter right child of 1: 
3
Enter left child of 3: 
-1
Enter right child of 3: 
-1

输出结果为：

Inorder traversal: 2 1 3 
Preorder traversal: 1 2 3 
Postorder traversal: 2 3 1