实验1 现代C++编程初体验

reverse修改原始序列，reverse_copy不修改；

rotate算法可以将元素移动到序列的另一个位置，first代表移动的起始位置。middle代表中间位置，last代表结束位置

#include <iostream>
#include <vector>
#include <algorithm>
#include <numeric>
#include <iomanip>
#include <cstdlib>
#include <ctime>
// 模板函数声明
template<typename T>
void output(const T& c);
int generate_random_number();
void test1();
void test2();
int main() {
    std::srand(std::time(0)); // 添加随机种子
    std::cout << "测试1: \n";
    test1();
        std::cout << "\n测试2: \n";
    test2();
}
// 输出容器对象c中的元素
template <typename T>
void output(const T& c) {
    for (auto& i : c)
        std::cout << i << ' ';
    std::cout << '\n';
}
// 返回[0, 100]区间内的一个随机整数
int generate_random_number() {
    return std::rand() % 101;
}
// 测试1：对容器类对象指定迭代器区间赋值、排序
void test1() {
    using namespace std;
    vector<int> v0(10); // 创建一个动态数组对象v0, 对象大小为10
    generate(v0.begin(), v0.end(), generate_random_number); // 生成随机数填充v0
    cout << "v0: "; output(v0);
    vector<int> v1{ v0 };
    sort(v1.begin(), v1.end()); // 对整个vector排序
    cout << "v1: "; output(v1);
    vector<int> v2{ v0 };
    sort(v2.begin() + 1, v2.end() - 1); // 只对中间部分排序，不包含首尾元素
    cout << "v2: "; output(v2);
}
// 测试2：对容器类对象指定迭代器区间赋值、计算最大值/最小值/均值
void test2() {
    using namespace std;
    vector<int> v0(10);
    generate(v0.begin(), v0.end(), generate_random_number);
    cout << "v0: "; output(v0);
    // 求最大值和最小值
    auto min_iter = min_element(v0.begin(), v0.end());
    auto max_iter = max_element(v0.begin(), v0.end());
    cout << "最小值: " << *min_iter << endl;
    cout << "最大值: " << *max_iter << endl;
    // 同时求最大值和最小值
    auto ans = minmax_element(v0.begin(), v0.end());
    cout << "最小值: " << *(ans.first) << endl;
    cout << "最大值: " << *(ans.second) << endl;
    // 求平均值
    double avg1 = accumulate(v0.begin(), v0.end(), 0.0) / v0.size();
    cout << "均值: " << fixed << setprecision(2) << avg1 << endl;
    sort(v0.begin(), v0.end());
    double avg2 = accumulate(v0.begin() + 1, v0.end() - 1, 0.0) / (v0.size() - 2);
    cout << "去掉最大值、最小值之后，均值: " << avg2 << endl;
}

1.generate算法用于填充一个范围内的元素。

2.效率高，代码更简洁

#include <string>
#include <algorithm>
#include <cctype>
#include<iostream>
unsigned char func(unsigned char c);
void test1();
void test2();
int main() {
    std::cout << "测试1: 字符串大小写转换\n";
    test1();
    std::cout << "\n测试2: 字符变换\n";
    test2();
}
unsigned char func(unsigned char c) {
    if (c == 'z')
        return 'a';
    if (c == 'Z')
        return 'A';
    if (std::isalpha(c))
        return static_cast<unsigned char>(c + 1);
    return c;
}
void test1() {
    std::string s1{ "Hello World 2049!" };
    std::cout << "s1 = " << s1 << '\n';
    std::string s2;
    for (auto c : s1)
        s2 += std::tolower(c);
    std::cout << "s2 = " << s2 << '\n';
    std::string s3;
    for (auto c : s1)
        s3 += std::toupper(c);
    std::cout << "s3 = " << s3 << '\n';
}
void test2() {
    std::string s1{ "I love cosmos!" };
    std::cout << "s1 = " << s1 << '\n';
    std::string s2(s1.size(), ' ');
    std::transform(s1.begin(), s1.end(),
        s2.begin(),
        func);
    std::cout << "s2 = " << s2 << '\n';
}

func对输入的字符进行变换

tolower将字符转换成小写形式，toupper转换成大写形式

四个参数的意义如下：

1. s1.begin()：输入范围的起始迭代器。
2. s1.end()：输入范围的结束迭代器
3. s2.begin()：输出范围的起始迭代器
4. func：对输入范围内的每个元素调用的函数。

区别：原代码是将结果存储到s2中，s1不变；修改后变换结果直接写回s1，覆盖原始内容

#include <iostream>
#include <string>
#include <algorithm>
#include <cctype>

// 区分大小写的回文判断
bool is_palindrome(const std::string& s) {
    int left = 0;
    int right = s.size() - 1;
    while (left < right) {
        if (s[left] != s[right]) {
            return false;
        }
        left++;
        right--;
    }
    return true;
}

// 不区分大小写的回文判断
bool is_palindrome_ignore_case(const std::string& s) {
    std::string temp = s;
    // 转换为小写
    std::transform(temp.begin(), temp.end(), temp.begin(), ::tolower);
    return is_palindrome(temp);
}

int main() {
    using namespace std;
    string s;
    // 多组输入，直到按下Ctrl+Z结束测试
    while (getline(cin, s)) {
        cout << boolalpha
            << "区分大小写: " << is_palindrome(s) << "\n"
            << "不区分大小写: " << is_palindrome_ignore_case(s) << "\n\n";
    }
}

使用 getline(cin, s) 替代 cin >> s，可以读取整行输入

#include <iostream>
#include <string>
#include <algorithm>

std::string dec2n(int x, int n = 2) {
    if (x == 0) return "0"; // 处理0的情况
    if (n < 2 || n > 36) return ""; // 检查进制范围

    std::string result;
    while (x > 0) {
        int remainder = x % n;
        char digit;
        if (remainder < 10) {
            digit = '0' + remainder;
        }
        else {
            digit = 'A' + (remainder - 10);
        }
        result.push_back(digit);
        x /= n;
    }
    std::reverse(result.begin(), result.end()); // 反转字符串
    return result;
}

int main() {
    int x;
    while (std::cin >> x) {
        std::cout << "十进制: " << x << '\n'
            << "二进制: " << dec2n(x) << '\n'
            << "八进制: " << dec2n(x, 8) << '\n'
            << "十二进制: " << dec2n(x, 12) << '\n'
            << "十六进制: " << dec2n(x, 16) << '\n'
            << "三十二进制: " << dec2n(x, 32) << "\n\n";
    }
}

#include <iostream>
#include <iomanip>
int main() {
    for (int i = 0; i < 27; i++) {
        if (i) for (int j = 0; j < 26; j++) std::cout << std::setw(2) << char('A' + (i + j) % 26);
        else for (int j = 0; j < 26; j++) std::cout << std::setw(2) << char('a' + j);
        std::cout << '\n';
    }
}

#include <iostream>
#include <cstdlib>
#include <ctime>
#include <iomanip>
using namespace std;

int main() {
    srand(time(0));
    int correct = 0;

    for (int i = 0; i < 10; i++) {
        int a = rand() % 10 + 1;
        int b = rand() % 10 + 1;
        int op = rand() % 4;
        char op_char;
        int result, answer;

        switch (op) {
        case 0: // 加法
            op_char = '+';
            result = a + b;
            break;
        case 1: // 减法
            op_char = '-';
            if (a < b) swap(a, b);
            result = a - b;
            break;
        case 2: // 乘法
            op_char = '*';
            result = a * b;
            break;
        case 3: // 除法
            op_char = '/';
            b = rand() % 10 + 1;
            a = b * (rand() % 10 + 1);
            while (a > 10) {
                b = rand() % 10 + 1;
                a = b * (rand() % 5 + 1);
            }
            result = a / b;
            break;
        }

        cout << a << " " << op_char << " " << b << " = ";
        cin >> answer;

        if (answer == result) {
            correct++;
        }
    }

    double accuracy = (correct * 100.0) / 10;
    cout << fixed << setprecision(2);
    cout << "正确率: " << accuracy << "%" << endl;

    return 0;
}