实验一

任务

 

源代码

// 现代C++标准库、算法库体验
// 本例用到以下内容:
// 1. 字符串string, 动态数组容器类vector、迭代器
// 2. 算法库：反转元素次序、旋转元素
// 3. 函数模板、const引用作为形参

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

// 模板函数声明
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();
}

// 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';
}

// 测试1：组合使用算法库、迭代器、string反转字符串
void test1() {
    using namespace std;

    string s0{"0123456789"};
    cout << "s0 = " << s0 << endl;

    string s1(s0);
    // 反转s1自身
    reverse(s1.begin(), s1.end());  
    cout << "s1 = " << s1 << endl;

    string s2(s0.size(), ' ');
    // 将s0反转后结果拷贝到s2, s0自身不变
    reverse_copy(s0.begin(), s0.end(), s2.begin()); 
    cout << "s2 = " << s2 << endl;
}

// 测试2：组合使用算法库、迭代器、vector反转动态数组对象vector内数据
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);
}

// 测试3：组合使用算法库、迭代器、vector实现元素旋转移位
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};
    // 将[v1.begin(), v1.end())区间内元素循环左移1位
    rotate(v1.begin(), v1.begin()+1, v1.end());  
    cout << "v1: "; output(v1);

    vector<int> v2{v0}; 
    // 将[v1.begin(), v1.end())区间内元素循环左移2位
    rotate(v2.begin(), v2.begin()+2, v2.end());  
    cout << "v2: "; output(v2);

    vector<int> v3{v0};
    // 将[v1.begin(), v1.end())区间内元素循环右移1位
    rotate(v3.begin(), v3.end()-1, v3.end()); 
     cout << "v3: "; output(v3);

    vector<int> v4{v0};
    // 将[v1.begin(), v1.end())区间内元素循环右移2位
    rotate(v4.begin(), v4.end()-2, v4.end()); 
    cout << "v4: "; output(v4);
}

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任务2

源代码

#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;
}

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任务3

源代码

#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';
}

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任务4

源代码

 

#include <iostream>
#include <string>
#include <algorithm>
using namespace std;
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 = 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)
{
    int l = 0, r = s.size() - 1;
    while(l < r)
    {
        if(tolower(s[l]) != tolower(s[r]))
            return false;
        l++;
        r--;
    }
    return true;
}

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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";
    }
    std::string table = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ";
    std::string res;
    while(x > 0)
    {
        int rem = x % n;
        res += table[rem];
        x = x / n;
    }
    std::reverse(res.begin(), res.end());
    return res;
}

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任务6

源代码

#include <iostream>
using namespace std;
 
int main()
{
    cout << "  ";
    for(char c = 'a'; c <= 'z'; c++)
    {
        cout << c << " ";
    }
    cout << endl;
    for(int i = 1; i <= 26; i++)
    {
        cout << i << " ";
        for(char ch = 'a'; ch <= 'z'; ch++)
        {
            char cipher = 'A' + (ch - 'a' + i) % 26;
            cout << cipher << " ";
        }
        cout << endl;
    }
    return 0;
}

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任务7

源代码

#include <iostream>
#include <cstdlib>
#include <ctime>
#include <iomanip>
using namespace std;
 
int main()
{
    srand((unsigned int)time(0));
    int correct = 0;
    int userAns, realAns;
    int a, b, op;
    char opChar;
 
    for(int i = 0; i < 10; i++)
    {
        op = rand() % 4;
        switch(op)
        {
            case 0:
                opChar = '+';
                a = rand()%10 +1;
                b = rand()%10 +1;
                realAns = a + b;
                break;
            case 1:
                opChar = '-';
                a = rand()%10 +1;
                b = rand()%10 +1;
                if(a < b) swap(a,b);
                realAns = a - b;
                break;
            case 2:
                opChar = '*';
                a = rand()%10 +1;
                b = rand()%10 +1;
                realAns = a * b;
                break;
            case 3:
                opChar = '/';
                do{
                    a = rand()%10 +1;
                    b = rand()%10 +1;
                }while(a % b != 0);
                realAns = a / b;
                break;
        }
        cout << a << " " << opChar << " " << b << " = ";
        cin >> userAns;
        if(userAns == realAns)
        {
            correct++;
        }
    }
    double rate = correct / 10.0;
    cout << "正确率: " << fixed << setprecision(2) << rate*100 << "%" << endl;
    return 0;
}

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