#define _CRT_SECURE_NO_WARNINGS
#include <cstdio> //标准输入输出函数
#include <cmath>
#include <cstring> //字符串处理函数
int main() {
printf("hello\n");
double x = 3.14;
printf("%lf %lf\n", sqrt(x), sin(x));
char s[10] = "hello";
puts(s);
char s2[16];
strcpy(s2, "world");
puts(s2);
strcat(s2, "sdfsdf");
puts(s2);
printf("%d %d\n", strlen(s), strlen(s2));
return 0;
}
#define _CRT_SECURE_NO_WARNINGS
#include <cstdio> //标准输入输出函数
#include <cstring> //字符串处理函数
#include <malloc.h>
int main() {
# if 1
char s[10];
strcpy(s, "hello");
puts(s);
#else
char *s = (char *)malloc(12 * sizeof(char));
strcpy(s, "hello world");
puts(s);
#endif
}
#include <iostream> //C++标准输入输出流头文件
using namespace std;
int main() {
cout << "hello world!"<< endl;
cout << "https://a.hwdong.com" << endl;
cout << 3+4 << endl;
double radius;
std::cin >> radius; //标准输入流对象cin 输入运算符>>
cout << 3.14*radius*radius;
std::cout << " *\n";
std::cout << " * *\n";
std::cout << " * *\n";
return 0;
}
#include <iostream>
using namespace std;
void help() {
cout << "=========简单计算器=========\n";
cout << "请输入：左运算数 运算符 右运算符\n";
}
int main() {
while (1) {
help();
double a, b;
char op;
cin >> a >> op >> b;
if (op == '+')
cout << a + b << endl;
//...补充你的代码
}
}
#include <fstream>
#include <iostream>
#include <string>
using namespace std;
int main() {
ofstream oF("test.txt");
oF << 3.14 << " " << "hello world\n";
oF.close();
ifstream iF("test.txt");
double d;
string str;
iF >> d >> str;
cout<<d <<" "<< str<<endl;
return 0;
}
#include <iostream>
using namespace std;
int main() {
int a = 3, &r = a;
cout << a << '\t' << r << endl;
r = 5;
cout << a << '\t' << r << endl;
return 0;
}
#include <iostream>
using namespace std;
void swap(int x, int y) {
cout << x << '\t' << y << endl;
int t = x;
x = y;
y = t;
cout << x << '\t' << y << endl;
}
int main() {
int a = 3, b = 4;
cout << a << '\t' << b << endl;
swap(a, b);
cout << a << '\t' << b << endl;
}
void swap(int *x, int *y) {
int t = *x;
*x = *y;
*y = t;
}
#include <iostream>
using namespace std;
int main() {
int a = 3, b = 4;
cout << a << '\t' << b << endl;
swap(&a, &b);
cout << a << '\t' << b << endl;
}
void swap(int &x, int &y) {
int t = x;
x = y;
y = t;
}
#include <iostream>
using namespace std;
int main() {
int a = 3, b = 4;
cout << a << '\t' << b << endl;
swap(a, b);
cout << a << '\t' << b << endl;
}
#include <iostream>
using namespace std;
void print(char ch, int n = 1) {
for (int i = 0; i < n; i++)
cout << ch;
}
int main() {
print('*'); cout << endl;
print('*',3); cout << endl;
print('*',5); cout << endl;
}
#include <iostream>
using namespace std;
int add(int x,int y=2,int z=3) {
return x + y + z;
}
int main() {
cout << add(5)<<endl;
cout << add(5,7) << endl;
cout << add(5,7,9) << endl;
}
#include <iostream>
using namespace std;
int add(int x, int y = 2) {
return x + y ;
}
double add(double x, double y = 2.0) {
return x + y;
}
int main() {
cout << add(5,3) << endl;
cout << add(5.3, 7.8) << endl;
cout << add((double)5, 7.8) << endl;//歧义性
}
#include <iostream>
using namespace std;
int add(int x, int y) {
return x + y;
}
double add(double x, double y ) {
return x + y;
}
int main() {
cout << add(5, 3) << endl;
cout << add(5.3, 7.8) << endl;
// cout << add("hello", "world") << endl;
}
#include <iostream>
#include <string>
using namespace std;
template<typename T>
T add(T x, T y) {
return x + y;
}
int main() {
/*
cout << add<int>(5, 3) << endl;
cout << add<double>(5.3, 7.8) << endl;
cout << add<int>(4, 6) << endl;
cout << add<string>("hello", "world") << endl;
*/
cout << add(5, 3) << endl;
cout << add(5.3, 7.8) << endl;
cout << add((double)5, 7.8) << endl; //歧义性
}
#include <iostream>
#include <string>
using namespace std;
int main() {
string s = "hello", s2("world");
//访问运算符.
cout << s.size() << endl;
string s3 = s.substr(1, 3);
cout << s3<< endl;
string s4 = s + " " + s2;
cout << s4 << endl; //"hello world"
s4[0] = 'H';
s4[6] = 'X';
cout << s4 << endl;
int pos = s4.find("orl");
cout << pos << endl;
s4.insert(3, "ABCDE");
cout << s4 << endl;
for (int i = 0; i < s4.size(); i++)
cout << s4[i] << "-";
cout << "\n";
}
#include <iostream>
using std::cout;
int main() {
int arr[] = { 10,20,30,40 }; //大小固定，以后不能添加更多int值
for (int i = 0; i < 4; i++)
cout << arr[i] << '\t';
cout << '\n';
}
#include <iostream>
#include <vector>
using namespace std;
int main() {
vector<int> v = { 7, 5, 16, 8 };
//push_back()，最后添加一个元素
v.push_back(25);
v.push_back(13);
//成员函数size()、下标运算符[]
for (int i = 0; i < v.size(); i++)
cout << v[i] << '\t';
cout << '\n';
v.pop_back();
for (int i = 0; i < v.size(); i++)
cout << v[i] << '\t';
cout << '\n';
v.resize(2);
for (int i = 0; i < v.size(); i++)
cout << v[i] << '\t';
cout << '\n';
}
/*
指针就是地址，变量的指针就是变量的地址。
指针变量就是存储指针（地址）的变量。
*/
#include <iostream>
using namespace std;
int main() {
int a=3;
int *p = &a; //取地址运算符&用于获得a的地址：&a
cout << p << '\t' << &a << endl;
//取内容运算符*用于获得指针指向的变量(内存块)
cout << *p << '\t' << a << endl; //*p就是a
*p = 5; //即a = 5;
cout << *p << '\t' << a << endl;
int *q = p; //q和p值相同，都是a的地址(指针)
cout << *p << '\t' << *q << '\t' << a << endl;
char *s = &a; //int *
}
/*
用指针访问数组元素
*/
#include <iostream>
using namespace std;
int main() {
int arr[] = { 10,20,30,40 };
int *p = arr;//数组名就是数组第一个元素的地址，即arr等于&(arr[0])
// p[i]就是*(p+i)
cout << *(p + 2) << '\t' << p[2] << '\t' << arr[2] << endl;
for (int *q = p + 4; p < q; p++)
cout << *p << '\t';
cout << '\n';
}
/*
malloc free realloc
动态内存分配：new用于申请内存块、delete用于释放内存块
T *p = new T;
delete p;
T *q = new T[5];
delete[] q;
*/
// 堆存储区
#include <iostream>
using namespace std;
int main() {
int *p = new int;
*p = 3;
cout << p << '\t' << *p << endl;
delete p; //内存泄漏
p = new int;
*p = 5;
cout << p << '\t' << *p << endl;
delete p;
}
#include <iostream>
using namespace std;
int main() {
int n = 4;
int *p = new int[n];
for (int i = 0; i < n; i++)
p[i] = 2 * i + 1;
for (int *q = p + n; p < q; p++)
cout << *p << '\t';
cout << '\n';
char *s = (char *)p;
char ch = 'A';
int n2 = n * sizeof(int) / sizeof(char);
for (int i = 0; i < n2; i++)
s[i] = ch + i;
for (char *r = s+n2; s < r; s++)
cout << *s;
cout << '\n';
delete[] p;
}
/*
输入一组学生成绩(姓名和分数)，输出：平均成绩、最高分和最低分。
当然，也要能输出所有学生信息
*/
#include <iostream>
#include <string>
#include <vector>
using namespace std;
struct student{
string name;
double score;
void print();
};
void student::print() {
cout << name << " " << score << endl;
}
int main() {
/*
student stu;
stu.name = "Li Ping";
stu.score = 78.5;
stu.print();
*/
vector<student> students;
while (1) {
student stu;
cout << "请输入姓名 分数:\n";
cin >> stu.name >> stu.score;
if (stu.score < 0) break;
students.push_back(stu);
}
for (int i = 0; i < students.size(); i++)
students[i].print();
double min = 100, max=0, average = 0;
for (int i = 0; i < students.size(); i++) {
if (students[i].score < min) min = students[i].score;
if (students[i].score > max) max = students[i].score;
average += students[i].score;
}
average /= students.size();
cout << "平均分、最高分、最低分："
<< average << " " << max << " " << min << endl;
}
/*
this指针: 成员函数实际上隐含一个this指针。
*/
#include <iostream>
#include <string>
using namespace std;
struct student {
string name;
double score;
void print() {
cout << this->name << " " << this->score << endl;
}
};
int main() {
student stu;
stu.name = "Li Ping";
stu.score = 78.5;
stu.print(); // print(&stu);
}
/*
struct和class区别：
struct里的成员默认是public(公开的)
class里的成员默认是private(私有的)
*/
#include <iostream>
#include <string>
using namespace std;
class student{
public: //接口
void print() {
cout << this->name << " " << this->score << endl;
}
string get_name() { return name; }
double get_score() { return score; }
void set_name(string n) { name = n; }
void set_score(double s) { score = s; }
private:
string name;
double score;
};
int main() {
student stu;
// stu.name = "Li Ping";
// stu.score = 78.5;
stu.set_name("Li Ping");
stu.set_score(78.5);
stu.print(); // print(&stu);
cout << stu.get_name() << " " << stu.get_score() << endl;
}
/*
构造函数： 函数名和类名相同且无返回类型的成员函数。
*/
#include <iostream>
#include <string>
using namespace std;
class student{
string name;
double score;
public:
student(string n,double s){ //不是默认构造函数
name = n; score = s;
cout << "构造函数\n";
}
void print() {
cout << this->name << " " << this->score << endl;
}
};
int main() {
student stu("LiPing",80.5); //在创建一个类对象时会自动调用称为“构造函数”的成员函数
stu.print();
student students[3];
}
/* 运算符重载：针对用户定义类型重新定义运算符函数
*/
#include <iostream>
#include <string>
using namespace std;
class student {
string name;
double score;
public:
student(string n, double s) {
name = n; score = s;
}
//友元函数
friend ostream& operator<<(ostream &o, student s);
friend istream& operator>>(istream &in, student &s);
};
ostream& operator<<(ostream &o, student s) {
cout << s.name << "," << s.score << endl;
return o;
}
istream& operator>>(istream &in, student &s) {
in >> s.name >> s.score;
return in;
}
int main() {
student stu("LiPing", 80.5);
cin >> stu; //operator>>(cin,stu)
cout << stu; //operator<<(cout,stu)
}
#include <iostream>
#include <string>
using namespace std;
class Point{
double x, y;
public:
double operator[](int i) const{ //const函数
if (i == 0) return x;
else if (i == 1) return y;
else throw "下标非法!"; //抛出异常
}
double& operator[](int i) {
if (i == 0) return x;
else if (i == 1) return y;
else throw "下标非法!"; //抛出异常
}
Point(double x_,double y_) {
x = x_; y = y_;
}
Point operator+(const Point q) {
return Point(this->x+q[0],this->y + q[1]);
}
//友元函数
friend ostream & operator<<(ostream &o, Point p);
friend istream & operator>>(istream &i, Point &p);
};
ostream & operator<<(ostream &o, Point p) {
o <<p.x << " " << p.y<< endl;
return o;
}
istream & operator>>(istream &i, Point &p) {
i >> p.x >> p.y;
return i;
}
/*
Point operator+(const Point p,const Point q) {
return Point(p[0] + q[0], p[1] + q[1]);
}
*/
int main() {
Point p(3.5, 4.8),q(2.0,3.0);
// cin >> p;
cout << p;
cout << p[0] << "-" << p[1] << endl; //p.operator[](0)
p[0] = 3.45; p[1] = 5.67;
cout << p;
cout << p<<q;
Point s = p + q; //p.operator+(q) vs operator+(p,q)
cout << s;
}
#include <iostream>
using namespace std;
class String {
char *data; //C风格的字符串
int n;
public:
~String() {
cout <<n<< " 析构函数!\n";
if(data)
delete[] data;
}
String(const String &s) { //硬拷贝
cout << "拷贝构造函数!\n";
data = new char[s.n + 1];
n = s.n;
for (int i = 0; i < n; i++)
data[i] = s.data[i];
data[n] = '\0';
}
String(const char *s=0) {
cout << "构造函数!\n";
if (s == 0) {
cout << "s==0\n";
data = 0; n = 0; return;
}
const char *p = s;
while (*p) p++;
n = p - s;
data = new char[n + 1];
for (int i = 0; i < n; i++)
data[i] = s[i];
data[n] = '\0';
}
int size() { return n; }
char operator[](int i)const {
if (i<0 || i>=n ) throw "下标非法";
return data[i];
}
char& operator[](int i) {
if (i < 0 || i >= n) throw "下标非法";
return data[i];
}
};
ostream & operator<<(ostream &o, String s) {
for (int i = 0; i < s.size(); i++)
cout << s[i];
return o;
}
void f() {
String str,str2("hello world");
str2[1] = 'E';
// cout << str2 << endl;
String s3 = str2; //拷贝构造函数
cout << s3 << endl;
s3[3] = 'L';
cout << s3 << endl;
cout << str2 << endl;
}
int main() {
f();
}
/*类
模拟vector<int>的类Vector
*/
#include <iostream>
#include <string>
using namespace std;
class student {
string name;
double score;
public:
student(string n="no", double s=0) {
name = n; score = s;
}
friend ostream& operator<<(ostream &o, student s);
};
ostream& operator<<(ostream &o, student s) {
cout << s.name << "," << s.score << endl;
return o;
}
//类模板
template<typename T>
class Vector {
T *data;
int capacity;
int n;
public:
Vector(int cap=3) {
data = new T[cap];
if (data == 0) {
cap = 0; n = 0;
return;
}
capacity = cap;
n = 0;
}
void push_back(T e) {
if (n == capacity) {//空间已经满
cout << "增加容量！\n";
T *p = new T[2 * capacity];
if (p) {
for (int i = 0; i < n; i++)
p[i] = data[i];
delete[] data;
data = p;
capacity = 2*capacity;
}
else {
return;
}
}
data[n] = e;
n++;
}
T operator[](int i) const{
if (i < 0 || i >= n) throw "下标非法!";
return data[i];
}
int size() {
return n;
}
};
int main() {
Vector<student> v;
v.push_back(student("Li",45.7));
v.push_back(student("Wang", 45.7));
v.push_back(student("zhao", 45.7));
for (int i = 0; i < v.size(); i++)
cout << v[i] ;
cout << endl;
v.push_back(student("zhang", 45.7));
v.push_back(student("Liu", 45.7));
for (int i = 0; i < v.size(); i++)
cout << v[i];
cout << endl;
}
int main() {
Vector<int> v;
v.push_back(3);
v.push_back(4);
v.push_back(5);
for(int i = 0 ; i<v.size();i++)
cout<<v[i]<<'\t';
cout << endl;
v.push_back(6);
v.push_back(7);
for (int i = 0; i < v.size(); i++)
cout << v[i] << '\t';
cout << endl;
}
int main() {
Vector<string> v;
v.push_back("hello");
v.push_back("world");
v.push_back("sdfasdf");
for (int i = 0; i < v.size(); i++)
cout << v[i] << '\t';
cout << endl;
v.push_back("ggg");
v.push_back("hhh");
for (int i = 0; i < v.size(); i++)
cout << v[i] << '\t';
cout << endl;
}
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