第10章 - 结构体和枚举

嗨，朋友！我是长安。

之前我们学习的数据类型（int、double、string等）只能存储单一类型的数据。但在实际开发中，我们经常需要把多个相关的数据组合在一起。

这一章，我们要学习结构体和枚举，它们能帮我们组织复杂的数据！

📦 什么是结构体？

生活中的例子

想象你要记录一个学生的信息：

  • 姓名：张三
  • 学号：1001
  • 年龄：20
  • 成绩：95.5

如果用变量存储：

string name = "张三";
int id = 1001;
int age = 20;
double score = 95.5;

这样太零散了！结构体可以把这些数据打包在一起：

struct Student {
    int id;
    string name;
    int age;
    double score;
};

🏗️ 定义和使用结构体

基本语法

struct 结构体名 {
    数据类型 成员1;
    数据类型 成员2;
    // ...
};

示例1：定义学生结构体

#include <iostream>
#include <string>
using namespace std;

// 定义结构体
struct Student {
    int id;
    string name;
    int age;
    double score;
};

int main() {
    // 创建结构体变量
    Student stu1;
    
    // 赋值
    stu1.id = 1001;
    stu1.name = "张三";
    stu1.age = 20;
    stu1.score = 95.5;
    
    // 输出
    cout << "学号：" << stu1.id << endl;
    cout << "姓名：" << stu1.name << endl;
    cout << "年龄：" << stu1.age << endl;
    cout << "成绩：" << stu1.score << endl;
    
    return 0;
}

示例2：结构体初始化

#include <iostream>
#include <string>
using namespace std;

struct Student {
    int id;
    string name;
    int age;
    double score;
};

int main() {
    // 方法1：定义时初始化
    Student stu1 = {1001, "张三", 20, 95.5};
    
    // 方法2：C++11列表初始化
    Student stu2{1002, "李四", 21, 88.0};
    
    // 方法3：部分初始化
    Student stu3 = {1003, "王五"};  // age和score为默认值
    
    cout << stu1.name << " - " << stu1.score << endl;
    cout << stu2.name << " - " << stu2.score << endl;
    cout << stu3.name << " - " << stu3.score << endl;
    
    return 0;
}

📚 结构体数组

#include <iostream>
#include <string>
using namespace std;

struct Student {
    int id;
    string name;
    double score;
};

int main() {
    // 结构体数组
    Student students[3] = {
        {1001, "张三", 95.5},
        {1002, "李四", 88.0},
        {1003, "王五", 92.0}
    };
    
    cout << "学生列表：" << endl;
    for (int i = 0; i < 3; i++) {
        cout << students[i].id << "\t"
             << students[i].name << "\t"
             << students[i].score << endl;
    }
    
    return 0;
}

🔗 结构体指针

#include <iostream>
#include <string>
using namespace std;

struct Student {
    int id;
    string name;
    double score;
};

int main() {
    Student stu = {1001, "张三", 95.5};
    Student* ptr = &stu;
    
    // 方法1：通过解引用访问
    cout << (*ptr).name << endl;
    
    // 方法2：使用箭头运算符（推荐）
    cout << ptr->name << endl;
    cout << ptr->score << endl;
    
    return 0;
}

📤 结构体作为函数参数

值传递

#include <iostream>
#include <string>
using namespace std;

struct Student {
    int id;
    string name;
    double score;
};

void printStudent(Student s) {
    cout << s.id << " - " << s.name << " - " << s.score << endl;
}

int main() {
    Student stu = {1001, "张三", 95.5};
    printStudent(stu);
    
    return 0;
}

引用传递（推荐）

void printStudent(const Student& s) {
    cout << s.id << " - " << s.name << " - " << s.score << endl;
}

指针传递

void printStudent(const Student* s) {
    cout << s->id << " - " << s->name << " - " << s->score << endl;
}

🔢 什么是枚举？

枚举（enum）是一种用户定义的数据类型，用来定义一组命名的常量。

生活中的例子

星期：

enum Weekday {
    MONDAY,     // 0
    TUESDAY,    // 1
    WEDNESDAY,  // 2
    THURSDAY,   // 3
    FRIDAY,     // 4
    SATURDAY,   // 5
    SUNDAY      // 6
};

📝 枚举的定义和使用

基本语法

enum 枚举名 {
    常量1,
    常量2,
    常量3
};

示例1：定义星期枚举

#include <iostream>
using namespace std;

enum Weekday {
    MONDAY,
    TUESDAY,
    WEDNESDAY,
    THURSDAY,
    FRIDAY,
    SATURDAY,
    SUNDAY
};

int main() {
    Weekday today = WEDNESDAY;
    
    cout << "今天是：";
    switch (today) {
        case MONDAY:
            cout << "星期一" << endl;
            break;
        case TUESDAY:
            cout << "星期二" << endl;
            break;
        case WEDNESDAY:
            cout << "星期三" << endl;
            break;
        case THURSDAY:
            cout << "星期四" << endl;
            break;
        case FRIDAY:
            cout << "星期五" << endl;
            break;
        case SATURDAY:
            cout << "星期六" << endl;
            break;
        case SUNDAY:
            cout << "星期日" << endl;
            break;
    }
    
    return 0;
}

示例2：自定义枚举值

#include <iostream>
using namespace std;

enum Color {
    RED = 1,
    GREEN = 2,
    BLUE = 3
};

enum Level {
    EASY = 1,
    NORMAL = 5,
    HARD = 10
};

int main() {
    Color myColor = RED;
    Level gameLevel = HARD;
    
    cout << "颜色值：" << myColor << endl;
    cout << "难度值：" << gameLevel << endl;
    
    return 0;
}

🌟 实战案例

案例1：学生管理系统（使用结构体）

#include <iostream>
#include <string>
using namespace std;

struct Student {
    int id;
    string name;
    int age;
    double score;
};

void printStudent(const Student& s) {
    cout << "学号：" << s.id << endl;
    cout << "姓名：" << s.name << endl;
    cout << "年龄：" << s.age << endl;
    cout << "成绩：" << s.score << endl;
}

void modifyScore(Student& s, double newScore) {
    s.score = newScore;
}

int main() {
    Student stu = {1001, "张三", 20, 85.0};
    
    cout << "修改前：" << endl;
    printStudent(stu);
    
    modifyScore(stu, 95.0);
    
    cout << "\n修改后：" << endl;
    printStudent(stu);
    
    return 0;
}

案例2：图书管理（结构体+枚举）

#include <iostream>
#include <string>
using namespace std;

enum BookStatus {
    AVAILABLE,    // 可借
    BORROWED,     // 已借出
    LOST          // 丢失
};

struct Book {
    int id;
    string title;
    string author;
    BookStatus status;
};

void printBook(const Book& book) {
    cout << "ID: " << book.id << endl;
    cout << "书名: " << book.title << endl;
    cout << "作者: " << book.author << endl;
    cout << "状态: ";
    
    switch (book.status) {
        case AVAILABLE:
            cout << "可借" << endl;
            break;
        case BORROWED:
            cout << "已借出" << endl;
            break;
        case LOST:
            cout << "丢失" << endl;
            break;
    }
}

int main() {
    Book books[3] = {
        {1001, "C++ Primer", "Stanley B. Lippman", AVAILABLE},
        {1002, "Effective C++", "Scott Meyers", BORROWED},
        {1003, "The C++ Programming Language", "Bjarne Stroustrup", AVAILABLE}
    };
    
    cout << "图书列表：" << endl;
    for (int i = 0; i < 3; i++) {
        cout << "\n========== 图书 " << (i + 1) << " ==========" << endl;
        printBook(books[i]);
    }
    
    return 0;
}

案例3：员工工资计算

#include <iostream>
#include <string>
using namespace std;

enum Position {
    INTERN,      // 实习生
    JUNIOR,      // 初级
    SENIOR,      // 高级
    MANAGER      // 经理
};

struct Employee {
    int id;
    string name;
    Position position;
    double baseSalary;
};

double calculateSalary(const Employee& emp) {
    double bonus = 0;
    
    switch (emp.position) {
        case INTERN:
            bonus = emp.baseSalary * 0.0;
            break;
        case JUNIOR:
            bonus = emp.baseSalary * 0.1;
            break;
        case SENIOR:
            bonus = emp.baseSalary * 0.2;
            break;
        case MANAGER:
            bonus = emp.baseSalary * 0.3;
            break;
    }
    
    return emp.baseSalary + bonus;
}

string getPositionName(Position pos) {
    switch (pos) {
        case INTERN: return "实习生";
        case JUNIOR: return "初级";
        case SENIOR: return "高级";
        case MANAGER: return "经理";
        default: return "未知";
    }
}

int main() {
    Employee employees[4] = {
        {1001, "张三", INTERN, 3000},
        {1002, "李四", JUNIOR, 5000},
        {1003, "王五", SENIOR, 8000},
        {1004, "赵六", MANAGER, 12000}
    };
    
    cout << "员工工资表：" << endl;
    cout << "ID\t姓名\t职位\t\t基本工资\t实发工资" << endl;
    cout << "--------------------------------------------------------" << endl;
    
    for (int i = 0; i < 4; i++) {
        cout << employees[i].id << "\t"
             << employees[i].name << "\t"
             << getPositionName(employees[i].position) << "\t\t"
             << employees[i].baseSalary << "\t\t"
             << calculateSalary(employees[i]) << endl;
    }
    
    return 0;
}

案例4：嵌套结构体

#include <iostream>
#include <string>
using namespace std;

struct Date {
    int year;
    int month;
    int day;
};

struct Person {
    string name;
    int age;
    Date birthday;  // 嵌套结构体
};

void printPerson(const Person& p) {
    cout << "姓名：" << p.name << endl;
    cout << "年龄：" << p.age << endl;
    cout << "生日：" << p.birthday.year << "年"
         << p.birthday.month << "月"
         << p.birthday.day << "日" << endl;
}

int main() {
    Person person = {
        "张三",
        20,
        {2004, 5, 15}
    };
    
    printPerson(person);
    
    return 0;
}

🎯 小结

概念说明示例
结构体定义组合多个数据struct Student { ... };
结构体变量创建实例Student stu;
成员访问使用点运算符stu.name
指针访问使用箭头运算符ptr->name
枚举定义定义常量集合enum Color { RED, GREEN };
枚举使用作为类型使用Color c = RED;

重要提醒：

  • ✅ 结构体可以包含任意类型的成员
  • ✅ 推荐使用const引用传递结构体
  • ✅ 枚举值默认从0开始
  • ✅ 枚举可以自定义值

💪 练习题

  1. 定义一个矩形结构体（包含长和宽），写函数计算面积和周长
  2. 定义一个日期结构体，写函数判断是否是闰年
  3. 创建一个商品结构体数组，实现按价格排序
  4. 使用枚举定义交通信号灯状态，模拟信号灯变化
  5. 定义一个复数结构体，实现复数的加减运算
点击查看参考答案

题目1 参考答案：

#include <iostream>
using namespace std;

struct Rectangle {
    double length;
    double width;
};

double getArea(const Rectangle& rect) {
    return rect.length * rect.width;
}

double getPerimeter(const Rectangle& rect) {
    return 2 * (rect.length + rect.width);
}

int main() {
    Rectangle rect = {10.5, 5.2};
    
    cout << "面积：" << getArea(rect) << endl;
    cout << "周长：" << getPerimeter(rect) << endl;
    
    return 0;
}

题目4 参考答案：

#include <iostream>
using namespace std;

enum TrafficLight {
    RED,
    YELLOW,
    GREEN
};

void printLight(TrafficLight light) {
    switch (light) {
        case RED:
            cout << "红灯 - 停止" << endl;
            break;
        case YELLOW:
            cout << "黄灯 - 准备" << endl;
            break;
        case GREEN:
            cout << "绿灯 - 通行" << endl;
            break;
    }
}

int main() {
    TrafficLight light = RED;
    
    for (int i = 0; i < 6; i++) {
        printLight(light);
        
        // 切换信号灯
        if (light == RED) {
            light = GREEN;
        } else if (light == GREEN) {
            light = YELLOW;
        } else {
            light = RED;
        }
    }
    
    return 0;
}

🚀 下一步

太棒了！你已经掌握了结构体和枚举的使用！

下一章，我们要学习文件操作，实现数据的持久化存储！

➡️ 第11章 - 文件操作

最近更新:
Contributors: 王长安