实验一
实验任务1
#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:
问题1:
reverse直接将字符串反转,reverse_copy将反转后的字符串复制到新的字符串,但不改变原字符串
问题2:
rotate将从begin为起点到begin+n之前的元素移动到end后面,第一、二个参数代表要移动的元素的范围,第三个参数代表移动到的位置
实验任务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:
问题1:
generate作用是给v0赋值
问题2:
minmax_element是代码效率更高,更简洁
问题3:
效果相同,lambda可以在需要函数的地方直接定义和使用
实验任务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:
问题1:
func函数的功能是将字母后移一位
问题2:
tolower的功能是将字母转换成小写,toupper的功能是将字母转换成大写
问题3:
transform的第一、二个参数是选择的范围,第三个参数是所选元素处理后移动到的位置,第四个参数是函数,对所选元素进行处理,第三个参数没改之前,s1不变,改为s1.begin()后,s1会被改为处理后的结果
实验任务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) { std::string s0{s}; reverse(s0.begin(),s0.end()); if(s0 == s) return true; return false; } bool is_palindrome_ignore_case(const std::string &s) { std::string s1; for(auto i:s) s1 += std::tolower(i); std::string s2{s1}; reverse(s1.begin(),s1.end()); if(s1 == s2) return true; return false; }
运行结果:
问题1:
使用std::getline函数
实验任务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) { std::string s; do { char c; int t = x % n; if(t < 10) c = '0' + t; else c = 'A' + t - 10; s.push_back(c); x /= n; }while(x > 0); reverse(s.begin(),s.end()); return s; }
运行结果:
实验任务6
#include <iostream> #include <iomanip> #include <string> #include <cctype> #include <algorithm> using namespace std; int main() { char s1[26]; for(int i = 0;i < 26;i++) s1[i] = 'a' + i; cout << " "; for(int i = 0;i < 26;i++) cout << " " << s1[i]; cout << "\n"; string s2; for(auto i:s1) s2 += toupper(i); for(int i = 1;i <= 26;i++) { cout << setw(2) << i; rotate(s2.begin(),s2.begin()+1,s2.end()); for(int j = 0;j < 26;j++) cout << " " << s2[j]; cout << "\n"; } }
运行结果:
实验任务7
#include <iostream> #include <cstdlib> #include <ctime> #include <iomanip> using namespace std; int main() { srand(time(0)); int t = 0; double s; for(int i = 0;i < 10;i++) { int a = rand()%10 + 1; int b = rand()%10 + 1; int x = rand()%4; int s1,s2; char c; switch(x) { case 0: c = '+'; s1 = a + b; break; case 1: while(a < b) { a = rand()%10 + 1; b = rand()%10 + 1; } c = '-'; s1 = a - b; break; case 2: c = '*'; s1 = a * b; break; case 3: c = '/'; while(a < b||a % b!=0) { a = rand()%10 + 1; b = rand()%10 + 1; } s1 = a / b; break; } cout << a << ' ' << c << ' ' << b << " = "; cin >> s2; if(s1 == s2) t++; } s = t * 10; cout << "正确率:" << fixed << setprecision(2) << s << '%'; }
运行结果: