第19章 - Vector 和 String

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

int main() {
    // 创建vector
    vector<int> nums;
    
    // 添加元素
    nums.push_back(10);
    nums.push_back(20);
    nums.push_back(30);
    
    // 访问元素
    cout << "第一个元素：" << nums[0] << endl;
    cout << "大小：" << nums.size() << endl;
    
    // 遍历
    for (int i = 0; i < nums.size(); i++) {
        cout << nums[i] << " ";
    }
    cout << endl;
    
    // 范围for循环
    for (int num : nums) {
        cout << num << " ";
    }
    cout << endl;
    
    // 删除最后一个元素
    nums.pop_back();
    
    // 清空
    nums.clear();
    
    return 0;
}

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

int main() {
    string str1 = "Hello";
    string str2 = "World";
    
    // 拼接
    string str3 = str1 + " " + str2;
    cout << str3 << endl;
    
    // 长度
    cout << "长度：" << str3.length() << endl;
    
    // 子串
    string sub = str3.substr(0, 5);  // "Hello"
    cout << "子串：" << sub << endl;
    
    // 查找
    size_t pos = str3.find("World");
    if (pos != string::npos) {
        cout << "找到位置：" << pos << endl;
    }
    
    // 替换
    str3.replace(0, 5, "Hi");
    cout << str3 << endl;
    
    // 比较
    if (str1 == "Hello") {
        cout << "字符串相等" << endl;
    }
    
    return 0;
}

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

struct Student {
    string name;
    double score;
};

int main() {
    vector<Student> students;
    
    // 添加学生
    students.push_back({"张三", 95.5});
    students.push_back({"李四", 88.0});
    students.push_back({"王五", 92.0});
    
    // 显示所有学生
    cout << "学生列表：" << endl;
    for (const auto& stu : students) {
        cout << stu.name << ": " << stu.score << endl;
    }
    
    // 计算平均分
    double sum = 0;
    for (const auto& stu : students) {
        sum += stu.score;
    }
    cout << "平均分：" << sum / students.size() << endl;
    
    return 0;
}