链表的建立与文件导入，及删除信息

为5个学生信息建立动态链表，每个学生包括 学号、姓名和分数3种信息（要求这些信息能 从文件中导入)，输入一个学号值删除列表中 该学号的学生节点。

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

#define MAX_LEN 20  // 学号、姓名的最大长度

// 学生信息结构体
struct student {
    char id[MAX_LEN];
    char name[MAX_LEN];
    int score;
    struct student *next;
};

// 从文件中读取学生信息并创建链表
struct student* read_students(const char* filename) {
    FILE *fp = fopen(filename, "r");
    if (fp == NULL) {
        printf("Failed to open file %s\n", filename);
        return NULL;
    }

    struct student *head = NULL, *tail = NULL;

    // 逐行读取文件内容，每行对应一个学生信息
    char line[MAX_LEN * 3 + 5];
    while (fgets(line, MAX_LEN * 3 + 5, fp) != NULL) {
        // 将一行内容拆分成学号、姓名和分数3个字段
        char id[MAX_LEN], name[MAX_LEN];
        int score;
        sscanf(line, "%s %s %d", id, name, &score);

        // 创建新节点并插入到链表尾部
        struct student *node = (struct student*) malloc(sizeof(struct student));
        strcpy(node->id, id);
        strcpy(node->name, name);
        node->score = score;
        node->next = NULL;

        if (head == NULL) {
            head = node;
        } else {
            tail->next = node;
        }
        tail = node;
    }

    fclose(fp);
    return head;
}

// 打印链表中的所有学生信息
void print_students(struct student *head) {
    printf("%-10s%-10s%-10s\n", "ID", "Name", "Score");
    printf("-----------------------------------\n");
    for (struct student *p = head; p != NULL; p = p->next) {
        printf("%-10s%-10s%-10d\n", p->id, p->name, p->score);
    }
}

// 在链表尾部插入新的学生信息
struct student* insert_student(struct student *head, const char *id, const char *name, int score) {
    // 创建新节点并插入到链表尾部
    struct student *node = (struct student*) malloc(sizeof(struct student));
    strcpy(node->id, id);
    strcpy(node->name, name);
    node->score = score;
    node->next = NULL;

    if (head == NULL) {
        head = node;
    } else {
        struct student *p = head;
        while (p->next != NULL) {
            p = p->next;
        }
        p->next = node;
    }

    return head;
}

// 删除学号为指定值的学生信息
struct student* delete_student(struct student *head, const char *id) {
    if (head == NULL) {
        return NULL;
    }

    struct student *prev = NULL, *p = head;
    while (p != NULL) {
        if (strcmp(p->id, id)==0)
        {
            prev->next = p->next;
            free(p);
        }
       else
       {
            prev = prev->next;
            p = prev->next;
        }
    }
    return head;
}