实验1

任务一：

#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1：reverse会改变原始数据，不需要重新分配内存，reverse_copy不会改变原始数据，是将反转结果复制到新的目标范围中，需要重新分配内存

问题2：rotate通过将序列在 middle 处分割并交换前后两部分来实现"循环移位"的效果，三个参数分别代表要旋转范围的开头，旋转后新序列的第一个元素，要旋转范围的末尾

任务2：

 #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1：generate的作用是用提供的函数反复调用来生成新值，并用这些新值覆盖指定范围内的所有元素。

问题2：minmax_element 的主要优势在于 效率，它比分别调用 min_element 和 max_element 要快得多。

问题3：对于简单、一次性、需要捕获上下文的逻辑，使用 Lambda 表达式，对于复杂、可重用、需要测试的逻辑，使用 自定义函数

任务3：

#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1：func的功能是将字母后移一位

问题2：tolower的功能是将大写字母转换为对应的小写字母，toupper的功能是将小写字母转换为对应的大写字母

问题3：第一个参数作用是输入范围的起始位置，第二个参数作用是输入范围的结束位置，第三个参数作用是输出目标的起始位置，第四个参数作用是操作函数，s2.begin()不会改变s1中的数据，改成s1.begin()会改变s1中的数据

任务4：

#include <iostream>
 #include <string>
 #include <algorithm>
 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)
{ if (s.empty()) return true;
std::string s2(s.size(), ' ');
reverse_copy(s.begin(), s.end(), s2.begin());
if(s==s2)
return true;
else return false;
}

bool is_palindrome_ignore_case(const std::string &s)
{  if (s.empty()) return true;
   std::string s1;
   for(auto c: s)
 s1+= std::tolower(c);
 std::string s2(s1.size(), ' ');
reverse_copy(s1.begin(), s1.end(), s2.begin());
if(s1==s2)
return true;
else return false;
}

运行结果截图：

问题回答：将 cin >> s 改为 getline(cin, s)

任务5：

#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)
{ if (x == 0) {
        return "0";
    }
    if (n < 2 || n > 36) {
        return "ERROR";  
    }
    std::string result;
    int num = x; 
    const char digits[] = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ";
    while (num > 0) {
        int remainder = num % n;  
        result += digits[remainder];  
        num /= n; 
    }
    std::reverse(result.begin(), result.end());
    return result;
}

运行结果截图：

任务6：

#include <iostream>
#include <string>

int main() {
    const std::string alphabet0= "abcdefghijklmnopqrstuvwxyz";
    std::cout<<"   ";
    for(int i=0;i<26;i++)
    {std::cout<< alphabet0[i] <<" ";
    } 
    std::cout << std::endl;
    std::string alphabet;
   for(auto c: alphabet0)
 alphabet+= std::toupper(c);
    
    for (int j = 1; j <= 26; j++) {
         if (j < 10) {
            std::cout << " ";
        }
        std::cout << j<<" ";
      
        for (int k = 0; k < 26; k++) {
            int new_pos = (k + j) % 26;
            std::cout << alphabet[new_pos]<<" ";
        }
        std::cout << std::endl;
    }
    return 0;
}

运行结果截图：

任务7：

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

int main() {
    srand(time(0));
    
    int correctCount = 0;
    const int totalQuestions = 10;for (int i = 1; i <= totalQuestions; i++) {
        int num1 = rand() % 10 + 1;  
        int num2 = rand() % 10 + 1; 

        int op = rand() % 4;
        char opChar;
        int correctAnswer;
        int userAnswer;

        switch (op) {
            case 0:
                opChar = '+';
                correctAnswer = num1 + num2;
                break;
                
            case 1: 
                opChar = '-';

                if (num1 < num2) {
                    std::swap(num1, num2);
                }
                correctAnswer = num1 - num2;
                break;
                
            case 2: 
                opChar = '*';
                correctAnswer = num1 * num2;
                break;
                
            case 3: 
                opChar = '/';
               
                if (num1 % num2 != 0) {
                 
                    do {
                        num2 = rand() % 9 + 1;  
                    } while (num1 % num2 != 0);
                }
                correctAnswer = num1 / num2;
                break;
        }
        
        std::cout << num1 << " " << opChar << " " << num2 << " = ";
        std::cin >> userAnswer;
 
        if (userAnswer == correctAnswer) {
            correctCount++;
        }
    }
    
    double accuracy = (static_cast<double>(correctCount) / totalQuestions) * 100;
    std::cout << std::fixed << std::setprecision(2);
    std::cout << "\n正确率：" << accuracy << "%" << std::endl;
    
    return 0;
}

运行结果截图：