实验1
任务一
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 << "\n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
观察与思考
1.reverse直接反转原容器，reverse_copy不改变原容器，而是将反转后的结果复制到目标容器里
2.rotate(first,middle,last),middle位置的元素，变成整个区间第一个元素
任务二
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
观察与思考
1.generate算法是反复调用第三个参数的函数，把函数返回值赋值给容器元素
2.minmax_element只需要遍历一次序列，而分别调用min_element，max_element需要遍历两次，前者更高效
3.不用单独写函数声明、函数定义，就地定义匿名函数，代码紧凑，这个生成逻辑只在这里使用，不用单独命名函数。这个 lambda 是匿名的，别的地方不能复用；如果多个地方要用同一个生成逻辑，独立函数更合适
任务三
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
观察与思考
1.如果字符是小写z → 返回a；如果字符是大写Z → 返回A；如果是普通英文字母（不是 Z/z），返回下一个字母（c+1，如a→b，M→N）；非字母字符（空格、!、数字等）直接原样返回
2.tolower(c)把英文字符转为小写；toupper(c)把英文字符转为大写
3.transform( first, last, result, op )，分别代表起始迭代器，末尾迭代器，目标容器的起始迭代器，变换函数（对源区间每个元素执行这个函数）
任务四
源代码
#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";
}
}
unsigned char to_lower_char(unsigned char c){
return std::tolower(c);
}
bool is_palindrome(const std::string &s){
std::string rev(s);
reverse(rev.begin(),rev.end());
return s==rev;
}
bool is_palindrome_ignore_case(const std::string &s){
std::string lower_s(s.size(),' ');
transform(s.begin(),s.end(),lower_s.begin(),to_lower_char);
std::string rev_lower(lower_s);
reverse(rev_lower.begin(),rev_lower.end());
return lower_s == rev_lower;
}
运行代码截图
观察与思考
用getline(cin,s)按行读，保留空格
任务五
源代码
#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){
const std::string table = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ";
if(x == 0){
return "0";
}
std::string res;
while(x>0){
int tem = x%n;
res += table[tem];
x/=n;
}
std::reverse(res.begin(),res.end());
return res;
}
运行结果截图
任务六
源代码
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#include <iostream>
using namespace std;
int main()
{
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" << endl;
for (int row = 1; row <= 26; ++row)
{
cout << (row < 10 ? " " : "") << row;
for (int col = 0; col < 26; ++col)
{
char ch = 'A' + (row - 1 + col) % 26;
cout << " " << ch;
}
cout << endl;
}
return 0;
}
运行结果截图
任务七
源代码
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#include <iostream>
#include <cstdlib>
#include <ctime>
#include <iomanip>
using namespace std;
int main()
{
srand(time(0));
int right = 0;
for (int t = 1; t <= 10; t++)
{
int a, b;
char op;
int ans;
int choose = rand() % 4;
if (choose == 0)
{
op = '+';
a = rand() % 10 + 1;
b = rand() % 10 + 1;
ans = a + b;
}
else if (choose == 1)
{
op = '-';
a = rand() % 10 + 1;
b = rand() % 10 + 1;
if (a < b)
{
int temp;
temp = a;
a = b;
b = temp;
}
ans = a - b;
}
else if (choose == 2)
{
op = '*';
a = rand() % 10 + 1;
b = rand() % 10 + 1;
ans = a * b;
}
else
{
op = '/';
while (true)
{
a = rand() % 10 + 1;
b = rand() % 10 + 1;
if (a % b == 0)
{
break;
}
}
ans = a / b;
}
int my_ans;
cout << a << " " << op << " " << b << " = ";
cin >> my_ans;
if (my_ans == ans)
{
right = right + 1;
}
}
double rate;
rate = right / 10.0 * 100;
cout << "正确率：" << fixed << setprecision(2) << rate << "%" << endl;
return 0;
}
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