使用C语音写出 首先，从记事本中依次读取每一行通讯录内容，将读取的所有教师信息按照年龄构建成二叉排序树，如图8-2所示。然后，分别通过对二叉排序树的先序遍历显示所有教师信息，通过二叉排序树的后序遍历按照姓名查询某位教师通讯信息，通过二叉排序树后序遍历按照部门查询该部门所有教师的通讯信息；最后，通过二叉排序树的中序遍历输出青年教师（≤35岁）通讯信息，遍历过程中，如果某个结点的年龄大于35岁，那么不再需要遍历该结点的右子树。

下面是使用C语言实现题目要求的代码，其中假设通讯录文件名为"contacts.txt"，每一行的格式为"姓名 年龄 部门 电话号码"，各字段之间用空格隔开：

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

#define MAX_NAME_LEN 20
#define MAX_DEPT_LEN 20
#define MAX_PHONE_LEN 20

typedef struct teacher {
    char name[MAX_NAME_LEN];
    int age;
    char dept[MAX_DEPT_LEN];
    char phone[MAX_PHONE_LEN];
} Teacher;

typedef struct bst_node {
    Teacher data;
    struct bst_node *left;
    struct bst_node *right;
} BSTNode;

void insert_bst_node(BSTNode **root, Teacher data);
void preorder_traversal(BSTNode *root);
BSTNode *search_bst_node(BSTNode *root, char *name);
void postorder_traversal_by_dept(BSTNode *root, char *dept);
void inorder_traversal_young_teachers(BSTNode *root);

int main() {
    FILE *fp;
    char line[100];
    BSTNode *root = NULL;

    fp = fopen("contacts.txt", "r");
    if (fp == NULL) {
        perror("Error opening contacts file");
        exit(EXIT_FAILURE);
    }

    while (fgets(line, sizeof(line), fp) != NULL) {
        Teacher t;
        sscanf(line, "%s %d %s %s", t.name, &t.age, t.dept, t.phone);
        insert_bst_node(&root, t);
    }

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

    char name[MAX_NAME_LEN];
    printf("Enter a name to search:\n");
    scanf("%s", name);
    BSTNode *node = search_bst_node(root, name);
    if (node != NULL) {
        printf("Found:\n%s %d %s %s\n", node->data.name, node->data.age, node->data.dept, node->data.phone);
    } else {
        printf("Not found\n");
    }

    char dept[MAX_DEPT_LEN];
    printf("Enter a department to search:\n");
    scanf("%s", dept);
    postorder_traversal_by_dept(root, dept);

    printf("Young teachers:\n");
    inorder_traversal_young_teachers(root);

    fclose(fp);
    return 0;
}

void insert_bst_node(BSTNode **root, Teacher data) {
    if (*root == NULL) {
        *root = (BSTNode *)malloc(sizeof(BSTNode));
        (*root)->data = data;
        (*root)->left = NULL;
        (*root)->right = NULL;
    } else if (data.age < (*root)->data.age) {
        insert_bst_node(&((*root)->left), data);
    } else {
        insert_bst_node(&((*root)->right), data);
    }
}

void preorder_traversal(BSTNode *root) {
    if (root != NULL) {
        printf("%s %d %s %s\n", root->data.name, root->data.age, root->data.dept, root->data.phone);
        preorder_traversal(root->left);
        preorder_traversal(root->right);
    }
}

BSTNode *search_bst_node(BSTNode *root, char *name) {
    if (root == NULL) {
        return NULL;
    } else if (strcmp(name, root->data.name) == 0) {
        return root;
    } else if (strcmp(name, root->data.name) < 0) {
        return search_bst_node(root->left, name);
    } else {
        return search_bst_node(root->right, name);
    }
}

void postorder_traversal_by_dept(BSTNode *root, char *dept) {
    if (root != NULL) {
        postorder_traversal_by_dept(root->left, dept);
        postorder_traversal_by_dept(root->right, dept);
        if (strcmp(dept, root->data.dept) == 0) {
            printf("%s %d %s %s\n", root->data.name, root->data.age, root->data.dept, root->data.phone);
        }
    }
}

void inorder_traversal_young_teachers(BSTNode *root) {
    if (root != NULL) {
        inorder_traversal_young_teachers(root->left);
        if (root->data.age <= 35) {
            printf("%s %d %s %s\n", root->data.name, root->data.age, root->data.dept, root->data.phone);
            inorder_traversal_young_teachers(root->right);
        }
    }
}

注：本代码仅作参考，可能存在不足之处，欢迎指正。