用c语言编程小学数学学习系统， 具有随机出题、自动评分、查看正确答案、错题重做等功能的测试系统。山 设计程序运行界面 用户登录功能一 能用菜单选择测试系统的各功能，写出代码

以下是一个简单的 C 语言实现，实现了基本的功能，可以根据实际需求进行改进：

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

// 存储用户信息
struct user {
    int score;
    struct question *questions;
};

struct user *users = NULL;
int num_users = 0;

// 生成随机题目
struct question {
    char *text;
    int answer;
};

struct question *generate_question() {
    static char text[50];
    struct question *q = (struct question*)malloc(sizeof(struct question));
    // 题目类型：加、减、乘、除
    char operators[] = {'+', '-', '*', '/'};
    char operator = operators[rand() % 4];
    
    // 生成两个操作数
    int a, b;
    if (operator == '+') {
        a = rand() % 100 + 1;
        b = rand() % 100 + 1;
    } else if (operator == '-') {
        a = rand() % 100 + 1;
        b = rand() % a + 1;
    } else if (operator == '*') {
        a = rand() % 10 + 1;
        b = rand() % 10 + 1;
    } else {
        b = rand() % 10 + 1;
        a = b * (rand() % 10 + 1);
    }
    
    // 生成题目字符串
    sprintf(text, "%d %c %d = ?", a, operator, b);
    // 计算正确答案
    if (operator == '/') {
        q->answer = a / b;
    } else {
        q->answer = eval(text);
    }
    q->text = (char*)malloc(strlen(text)+1);
    strcpy(q->text, text);
    
    return q;
}

// 用户登录
void login() {
    char username[20];
    printf("请输入用户名：");
    scanf("%s", username);
    for (int i = 0; i < num_users; i++) {
        if (strcmp(users[i].name, username) == 0) {
            printf("欢迎回来，%s\n", username);
            return;
        }
    }
    num_users++;
    users = (struct user*)realloc(users, num_users * sizeof(struct user));
    users[num_users-1].name = (char*)malloc(strlen(username)+1);
    strcpy(users[num_users-1].name, username);
    users[num_users-1].score = 0;
    users[num_users-1].questions = NULL;
    printf("欢迎新用户%s\n", username);
}

// 生成试卷
struct question **generate_paper() {
    struct question **paper = (struct question**)malloc(10 * sizeof(struct question*));
    for (int i = 0; i < 10; i++) {
        paper[i] = generate_question();
    }
    return paper;
}

// 开始考试
void start_exam() {
    int user_index = -1;
    for (int i = 0; i < num_users; i++) {
        if (strcmp(users[i].name, username) == 0) {
            user_index = i;
            break;
        }
    }
    if (user_index == -1) {
        printf("您还没有登录\n");
        return;
    }
    struct question **paper = generate_paper();
    int score = 0;
    users[user_index].questions = (struct question*)malloc(10 * sizeof(struct question));
    for (int i = 0; i < 10; i++) {
        printf("第%d题：%s", i+1, paper[i]->text);
        int user_answer;
        scanf("%d", &user_answer);
        if (user_answer == paper[i]->answer) {
            printf("回答正确！\n");
            score += 10;
        } else {
            printf("回答错误，正确答案是%d\n", paper[i]->answer);
        }
        users[user_index].questions[i] = *paper[i];
    }
    users[user_index].score += score;
    printf("考试结束，本次得分：%d\n", score);
}

// 查看历史成绩
void view_score() {
    int user_index = -1;
    for (int i = 0; i < num_users; i++) {
        if (strcmp(users[i].name, username) == 0) {
            user_index = i;
            break;
        }
    }
    if (user_index == -1) {
        printf("您还没有登录\n");
        return;
    }
    printf("您的历史成绩为：%d\n", users[user_index].score);
}

// 查看错题
void view_mistakes() {
    int user_index = -1;
    for (int i = 0; i < num_users; i++) {
        if (strcmp(users[i].name, username) == 0) {
            user_index = i;
            break;
        }
    }
    if (user_index == -1) {
        printf("您还没有登录\n");
        return;
    }
    int num_mistakes = 0;
    struct question *mistakes = (struct question*)malloc(10 * sizeof(struct question));
    for (int i = 0; i < 10; i++) {
        if (users[user_index].questions[i].answer != users[user_index].questions[i].user_answer) {
            mistakes[num_mistakes] = users[user_index].questions[i];
            num_mistakes++;
        }
    }
    if (num_mistakes == 0) {
        printf("恭喜您，没有错题！\n");
    } else {
        printf("您的错题如下：\n");
        for (int i = 0; i < num_mistakes; i++) {
            printf("题目：%s\n", mistakes[i].text);
            printf("您的答案：%d\n", mistakes[i].user_answer);
            printf("正确答案：%d\n", mistakes[i].answer);
        }
    }
}

// 主程序
int main() {
    srand(time(NULL));
    while (1) {
        printf("欢迎使用小学数学学习系统\n");
        printf("请选择要进行的操作：\n");
        printf("1. 登录\n");
        printf("2. 开始考试\n");
        printf("3. 查看历史成绩\n");
        printf("4. 查看错题\n");
        printf("5. 退出\n");
        int choice;
        scanf("%d", &choice);
        if (choice == 1) {
            login();
        } else if (choice == 2) {
            start_exam();
        } else if (choice == 3) {
            view_score();
        } else if (choice == 4) {
            view_mistakes();
        } else if (choice == 5) {
            printf("谢谢使用，再见！\n");
            break;
        } else {
            printf("无效的选择，请重新输入\n");
        }
    }
    return 0;
}