用C++代码定义一个包含学生信息（学号，姓名，成绩）的链表，使其具有如下功能

1. 插入学生信息
2. 删除学生信息
3. 修改学生信息
4. 查找学生信息
5. 输出所有学生信息
6. 退出程序

以下是基于C语言的实现代码：

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

// 学生结构体
typedef struct student {
    int id;         // 学号
    char name[20];  // 姓名
    float score;    // 成绩
    struct student *next;   // 下一个节点指针
} student_t;

// 创建新的学生节点
student_t *new_student(int id, char *name, float score) {
    student_t *node = (student_t *)malloc(sizeof(student_t));
    if (node == NULL) {
        printf("Error: out of memory\n");
        exit(1);
    }
    node->id = id;
    strcpy(node->name, name);
    node->score = score;
    node->next = NULL;
    return node;
}

// 插入学生信息
void insert_student(student_t **head, student_t *node) {
    if (*head == NULL) {
        // 链表为空，直接将节点插入
        *head = node;
    } else {
        // 遍历链表找到最后一个节点
        student_t *ptr = *head;
        while (ptr->next != NULL) {
            ptr = ptr->next;
        }
        // 将新节点插入到链表尾部
        ptr->next = node;
    }
}

// 删除学生信息
void delete_student(student_t **head, int id) {
    // 遍历链表查找要删除的节点
    student_t *ptr = *head;
    student_t *prev = NULL;
    while (ptr != NULL && ptr->id != id) {
        prev = ptr;
        ptr = ptr->next;
    }
    if (ptr == NULL) {
        printf("Error: student not found\n");
        return;
    }
    // 将要删除的节点从链表中断开
    if (prev == NULL) {
        *head = ptr->next;
    } else {
        prev->next = ptr->next;
    }
    free(ptr);
}

// 修改学生信息
void modify_student(student_t *head, int id, char *name, float score) {
    // 遍历链表查找要修改的节点
    student_t *ptr = head;
    while (ptr != NULL && ptr->id != id) {
        ptr = ptr->next;
    }
    if (ptr == NULL) {
        printf("Error: student not found\n");
        return;
    }
    // 修改节点信息
    strcpy(ptr->name, name);
    ptr->score = score;
}

// 查找学生信息
void find_student(student_t *head, int id) {
    // 遍历链表查找要查找的节点
    student_t *ptr = head;
    while (ptr != NULL && ptr->id != id) {
        ptr = ptr->next;
    }
    if (ptr == NULL) {
        printf("Error: student not found\n");
        return;
    }
    // 输出节点信息
    printf("ID: %d, Name: %s, Score: %.2f\n", ptr->id, ptr->name, ptr->score);
}

// 输出所有学生信息
void print_all_students(student_t *head) {
    // 遍历链表输出所有节点信息
    student_t *ptr = head;
    while (ptr != NULL) {
        printf("ID: %d, Name: %s, Score: %.2f\n", ptr->id, ptr->name, ptr->score);
        ptr = ptr->next;
    }
}

int main() {
    student_t *head = NULL;
    int choice, id;
    char name[20];
    float score;
    
    while (1) {
        printf("\n1. Insert student\n2. Delete student\n3. Modify student\n");
        printf("4. Find student\n5. Print all students\n6. Exit\n");
        printf("Enter your choice: ");
        scanf("%d", &choice);
        
        switch (choice) {
            case 1:
                printf("Enter student ID: ");
                scanf("%d", &id);
                printf("Enter student name: ");
                scanf("%s", name);
                printf("Enter student score: ");
                scanf("%f", &score);
                insert_student(&head, new_student(id, name, score));
                break;
            case 2:
                printf("Enter student ID to delete: ");
                scanf("%d", &id);
                delete_student(&head, id);
                break;
            case 3:
                printf("Enter student ID to modify: ");
                scanf("%d", &id);
                printf("Enter new name: ");
                scanf("%s", name);
                printf("Enter new score: ");
                scanf("%f", &score);
                modify_student(head, id, name, score);
                break;
            case 4:
                printf("Enter student ID to find: ");
                scanf("%d", &id);
                find_student(head, id);
                break;
            case 5:
                print_all_students(head);
                break;
            case 6:
                printf("Exiting program\n");
                exit(0);
            default:
                printf("Invalid choice\n");
        }
    }
    
    return 0;
}