代码

#define _CRT_SECURE_NO_WARNINGS#include <stdio.h>
#include <string.h>
void Save();struct SUser // 结构体定义
{int nNumb; // 学号char sName[20]; // 姓名float fMath; // 数学成绩
}g_user[100];void Print() // 打印子函数
{puts("\n学号\t姓名\t数学");int i = 0;while (g_user[i].nNumb){if(g_user[i].nNumb>0)printf("%d\t%s\t%0.1f\n", g_user[i].nNumb, g_user[i].sName, g_user[i].fMath);++i;}printf("\n\t总共有%d条学生信息\n\n", i);
}int Check(int nNumb) // 查找
{int i = 0;while (g_user[i].nNumb){if (nNumb == g_user[i].nNumb)return 1;++i;}return 0;
}void Add() // 增加
{int nNumb;printf("请输入学号：");scanf_s("%d", &nNumb);while (Check(nNumb)){printf("该学号已存在，请重新输入(0取消输入)：");scanf_s("%d", &nNumb);if (nNumb == 0)return;}int i = 0;while (g_user[i].nNumb>0)++i;//scanf("%d%s%f",&g_user[i].nNumb,)g_user[i].nNumb = nNumb;printf("请输入姓名：");scanf_s("%s", g_user[i].sName,sizeof(g_user[i].sName));printf("请输入成绩：");scanf_s("%f", &g_user[i].fMath);Save();Print();
}void Delete() // 删除
{printf("请输入要删除的学号：");int nNumb;scanf_s("%d", &nNumb);int i = 0;//int flag = 0;while (g_user[i].nNumb){if (g_user[i].nNumb == nNumb){//flag = 1;g_user[i].nNumb = -1;break;}++i;}//if (flag == 0)if (g_user[i].nNumb!=-1)//if (g_user[i].nNumb==0)puts("你输入的学号不存在！");else{Save();Print();}
}void Modify() // 修改
{printf("请输入要修改的学号：");int nNumb;scanf_s("%d", &nNumb);int i = 0;while (g_user[i].nNumb){if (g_user[i].nNumb == nNumb){printf("%d\t%s\t%0.1f\n", g_user[i].nNumb, g_user[i].sName, g_user[i].fMath);printf("请输入新的姓名：");scanf_s("%s", g_user[i].sName, sizeof(g_user[i].sName));printf("请输入新的成绩：");scanf_s("%f", &g_user[i].fMath);return;}++i;}Save();Print();
}void Load() // 加载保存的数据文件
{FILE* pf = fopen("data.lv", "r");if (!pf)return;int i = 0;while (fread(&g_user[i], 1, sizeof(SUser), pf) == sizeof(SUser))++i;fclose(pf);
}void Save() // 保存结构体数据到文件
{FILE* pf = fopen("data.lv", "w");if (!pf){puts("保存数据时失败！");return;}int i = 0;while (g_user[i].nNumb){if (-1 != g_user[i].nNumb)fwrite(&g_user[i], 1, sizeof(SUser), pf);++i;}fclose(pf);
}void SortByNumb() // 按学号排序
{int i = 0, n = 0;while (g_user[i++].nNumb > 0)++n;i = 0;while (i < n - 1){int j = 0;while (j < n - 1 - i){if (g_user[j].nNumb > g_user[j + 1].nNumb){SUser t = g_user[j];g_user[j] = g_user[j + 1];g_user[j + 1] = t;}++j;}++i;}
}void SortByName() // 按姓名排序
{int i = 0, n = 0;while (g_user[i++].nNumb)++n;i = 0;while (i < n - 1){int j = 0;while (j < n - 1 - i){if (strcmp(g_user[j].sName , g_user[j + 1].sName)>0){SUser t = g_user[j];g_user[j] = g_user[j + 1];g_user[j + 1] = t;}++j;}++i;}
}void SortByMath() // 按数学成绩排序
{int i = 0, n = 0;while (g_user[i++].nNumb)++n;i = 0;while (i < n - 1){int j = 0;while (j < n - 1 - i){if (g_user[j].fMath < g_user[j + 1].fMath){SUser t = g_user[j];g_user[j] = g_user[j + 1];g_user[j + 1] = t;}++j;}++i;}
}int DispMenu()
{puts("1.按学号排序");puts("2.按姓名排序");puts("3.按成绩排序");puts("0.返回主菜单");printf("请选择：");int i = 0;scanf_s("%d", &i);switch (i){case 1:SortByNumb();Print();break;case 2:SortByName();Print();break;case 3:SortByMath();Print();break;}return i;
}int Menu()
{int i = 0;puts("1.浏览所有信息");puts("2.添加信息");puts("3.删除信息");puts("4.修改信息");puts("5.查找信息");puts("0.退出");printf("请选择：");scanf_s("%d", &i);switch (i){case 0:break;case 1:while (DispMenu());Print();break;case 2:Add();break;case 3:Delete();break;case 4:Modify();break;}return i;
}int main()
{Load();while (Menu());return 0;
}

运行结果