实验1

• 任务1
  源代码：

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

template<typename T>
void output(const T &c);
void test1();
void test2();
void test3();

int main() {
    std::cout << "测试1: \n";
    test1();

    std::cout << "\n测试2: \n";
    test2();

    std::cout << "\n测试3: \n";
    test3();
}
template <typename T>
void output(const T &c) {
    for(auto &i : c)
        std::cout << i << ' ';
    std::cout << '\n';
}
void test1() {
    using namespace std;
    string s0{"0123456789"};
    cout << "s0 = " << s0 << endl;
    string s1(s0);
    reverse(s1.begin(), s1.end());
    cout << "s1 = " << s1 << endl;
    string s2(s0.size(), ' ');
    reverse_copy(s0.begin(), s0.end(), s2.begin());
    cout << "s2 = " << s2 << endl;
}
void test2() {
    using namespace std;
    vector<int> v0{2, 0, 4, 9};
    cout << "v0: "; output(v0);
    vector<int> v1{v0};
    reverse(v1.begin(), v1.end());
    cout << "v1: "; output(v1);
    vector<int> v2{v0};
    reverse_copy(v0.begin(), v0.end(), v2.begin());
    cout << "v2: "; output(v2);
}

void test3() {
    using namespace std;
    vector<int> v0{0, 1, 2, 3, 4, 5, 6, 7, 8, 9};
    cout << "v0: "; output(v0);
    vector<int> v1{v0};
    rotate(v1.begin(), v1.begin()+1, v1.end());
    cout << "v1: "; output(v1);
    vector<int> v2{v0};
    rotate(v2.begin(), v2.begin()+2, v2.end());
    cout << "v2: "; output(v2);
    vector<int> v3{v0};
    rotate(v3.begin(), v3.end()-1, v3.end());
    cout << "v3: "; output(v3);
    vector<int> v4{v0};
    rotate(v4.begin(), v4.end()-2, v4.end());
    cout << "v4: "; output(v4);
}

运行结果截图：

问题回答：
1.reverse是将原字符串直接反转，改变了原值；而reverse_copy是新生成一个反转后的字符串，不改变原值。
2.rotate(first,middle,last)以middle为分界线，分成前后两段，然后交换这两段的位置。
first：旋转序列起始位置
middle：分界线
last：旋转序列终点位置

• 任务2
  源代码：

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#include <iostream>
#include <vector>
#include <algorithm>
#include <numeric>
#include <iomanip>
#include <cstdlib>
#include <ctime>

template<typename T>
void output(const T &c);
int generate_random_number();
void test1();
void test2();
int main() {
    std::srand(std::time(0));
    std::cout << "测试1: \n";
    test1();
    std::cout << "\n测试2: \n";
    test2();
}
template <typename T>
void output(const T &c) {
    for(auto &i: c)
        std::cout << i << ' ';
    std::cout << '\n';
}
int generate_random_number() {
    return std::rand() % 101;
}
void test1() {
    using namespace std;
    vector<int> v0(10);
    generate(v0.begin(), v0.end(), generate_random_number);
    cout << "v0: "; output(v0);
    vector<int> v1{v0};
    sort(v1.begin(), v1.end());
    cout << "v1: "; output(v1);
    vector<int> v2{v0};
    sort(v2.begin()+1, v2.end()-1);
    cout << "v2: "; output(v2);
}

void test2() {
    using namespace std;
    vector<int> v0(10);
    generate(v0.begin(), v0.end(), generate_random_number);
    cout << "v0: "; output(v0);
    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;

    auto ans = minmax_element(v0.begin(), v0.end());
    cout << "最小值: " << *(ans.first) << endl;
    cout << "最大值: " << *(ans.second) << endl;

    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;
}

运行结果截图：

问题回答：
1.generate在指定容器和指定范围中随机生成一定量的数字
2.minmax_element只需要一次遍历即可获取最大、最小值
3.lambda表达式可以写在调用位置，不需要另外声明或定义函数。

• 任务3
  源代码：

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

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';
}

运行结果截图：

问题回答：
1.func可以将字母循环后移一位
2.tolower将大写字母转换为小写字母，toupper则相反
3.transform(s1.begin(),s1.end(),s2.begin(),func)，其中s1.begin()表示输入区间起点，s1.end()表示输入区间终点，s2.begin()表示输出结果的起始位置，func是对输入进行转换的函数。如果将第三个参数s2.begin()改成s1.begin()，则直接对原字符串进行修改

• 任务4
  源代码：

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

bool is_palindrome(const std::string &s);
bool is_palindrome_ignore_case(const std::string &s);

int main() {
    using namespace std;
    string s;

    while(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";
    }
}

bool is_palindrome(const std::string &s) {
    int l = 0, r = (int)s.size() - 1;
    while (l < r) {
        if (s[l] != s[r]) {
            return false;
        }
        l++;
        r--;
    }
    return true;
}
bool is_palindrome_ignore_case(const std::string &s) {
    std::string t = s;
    for (int i = 0; i < (int)t.size(); i++) {
        t[i] = std::tolower(t[i]);
    }
    return is_palindrome(t);
}

运行结果截图：

问题回答：
用getline函数读取一整行：
while (getline(cin, s)) {

• 任务5
  源代码：

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

std::string dec2n(int x, int n = 2);

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";
    }
}

std::string dec2n(int x, int n) {
    using namespace std;
    if (x == 0) return "0";
    string ans;
    while (x) {
        int t = x % n;
        if(t < 10) {
            ans += t + '0';
        }
        else ans += t - 10 + 'A';
        x /= n;
    }
    reverse(ans.begin(), ans.end());
    return ans;
}

运行结果截图：

• 任务6
  源代码：

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#include <iostream>
#include <string>
#include <algorithm>
#include <iomanip>   
int main() {
    std::string alphabet = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
    std::cout << "   a b c d e f g h i j k l m n o p q r s t u v w x y z\n";
    for (int i = 1; i <= 26; ++i) {
        std::rotate(alphabet.begin(), alphabet.begin() + 1, alphabet.end());
        std::cout << std::setw(2) << i << " ";
        for (char c : alphabet) {
            std::cout << c << " ";
        }
        std::cout << "\n";
    }
    return 0;
}

运行结果截图：

• 任务7
  源代码：

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#include <iostream>
#include <cstdlib>
#include <ctime>
#include <iomanip> 
#include <algorithm> 

using namespace std;

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

    for (int i = 0; i < 10; ++i) {
        int op = rand() % 4; 
        int a, b;
        char opChar;
        int correctAnswer;

        if (op == 3) {
            opChar = '/';
            b = rand() % 10 + 1;               
            int max_q = 10 / b;               
            int q = rand() % max_q + 1;       
            a = b * q;                  
            correctAnswer = a / b;
        } else {
          
            a = rand() % 10 + 1; 
            b = rand() % 10 + 1; 

            if (op == 0) {
                opChar = '+';
                correctAnswer = a + b;
            } else if (op == 1) {
                opChar = '-';
                if (a < b) {
                    swap(a, b); 
                }
                correctAnswer = a - b;
            } else if (op == 2) {
                opChar = '*';
                correctAnswer = a * b;
            }
        }

        
        cout << a << " " << opChar << " " << b << " = ";
        int userAnswer;
        cin >> userAnswer;
        if (userAnswer == correctAnswer) {
            correctCount++;
        }
    }
    double accuracy = (correctCount * 100.0) / 10.0;
    cout << "正确率: " << fixed << setprecision(2) << accuracy << "%" << endl;

    return 0;
}

运行结果截图：

实验总结：
这次实验（尤其是后几个自主编写代码任务）参考AI的代码风格，我逐渐发觉精简的变量名、注释的重要性，这有利于代码的编写和后期维护，并且在实际开发中体现的尤为明显。