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

typedef struct Node
{
    char  num[20];
    char name[20];
}STU;
void add();
void read(char *);
void delete();
void visit();
int main()
{
    while(1)
    {
        printf("1  add\n");
        printf("2  delete\n");
        int i;
        scanf("%d",&i);
        switch(i)
        {
            case 1:
                add();
                break;
            case 2:
            {
                visit();
                delete();
                printf("===========================\n");
                visit();
                break;
            }
            default:
                break;
        }
    }

    return 0;
}
void delete()
{   
    char p[128];
    char num[128];
    int i=0;
    FILE *fp=fopen("stu.txt","r+");   
    if(fp == NULL)
    {
        printf("文件不存在！\n");
        exit(1);
    }
    STU *stu2=(STU *)malloc(sizeof(STU));
   
    printf("输入需要删除的num!\n");
    scanf("%s",num);

    rewind(fp);
    while(1)
    {
        fseek(fp,i*sizeof(STU),SEEK_SET);
        fread(stu2,sizeof(STU),1,fp);
        if(strcmp(p,stu2->num)==0)
        {
            break;
        }
        if(strcmp(num,stu2->num)==0)
        {
            free(stu2);
            strcpy(stu2->num,"");
            strcpy(stu2->name,"");
            break;
        }
        strcpy(p,stu2->num);
        i++;
    }

    fclose(fp);
}
void add()
{
    FILE *fp=fopen("stu.txt","a+");   
    STU *stul=(STU *)malloc(sizeof(STU));
   
    printf("请输入编号：\n");
    scanf("%s",stul->num);
    printf("请输入姓名：\n");
    scanf("%s",stul->name);
   
    if(fgetc(fp) != EOF)
    {
        read(stul->num);
    }
    fwrite(stul,sizeof(STU),1,fp);

    fclose(fp);
}

void read(char *num)
{
    char p[128]="abcd";
    int i=0;
    FILE *fp = fopen("stu.txt","r");   
    STU *stu2=(STU *)malloc(sizeof(STU));
   
    rewind(fp);
    while(1)
    {
        fseek(fp,i*sizeof(STU),SEEK_SET);
        fread(stu2,sizeof(STU),1,fp);
        if(strcmp(p,stu2->num)==0)
        {
            break;
        }
        if(strcmp(num,stu2->num)==0)
        {
            printf("用户名已经存在！\n");
            break;
        }
        strcpy(p,stu2->num);
        i++;
    }
   
    fclose(fp);
}

void visit()
{
    char p[128]="abcd";
    int i=0;
    FILE *fp=fopen("stu.txt","r");   
    STU *stu2=(STU *)malloc(sizeof(STU));
   
    rewind(fp);
    while(1)
    {
        fseek(fp,i*sizeof(STU),SEEK_SET);
        fread(stu2,sizeof(STU),1,fp);
        if(strcmp(p,stu2->num)==0)
        {
            break;
        }
        printf("第%d次：%s  %s\n",i,stu2->num, stu2->name);
        strcpy(p,stu2->num);
        i++;
    }

    fclose(fp);   
}
不用链表，单是结构体好像不能进行修改删除动作，上述代码只是实现了读和写，删除没有实现，各位大大可否帮忙，谢谢了！