C++ IO库：cmd读写，字符串读写，文件读写，＜＜重载，标准输出
【摘要】
1、三个头文件
iostream: istream+ostream
//读写流
#include<iostream>
using namespace std;
int main(){
i...
1、三个头文件
iostream: istream+ostream
//读写流
#include<iostream>
using namespace std;
int main(){
int a, b;
cin>>a>>b;
cout<<a+b<<endl;
return 0;
}
fstream:ifstream+ofstream
//读写文件
#include<fstream>
using namespace std;
int main(){
int a, b, c;
ifstream in1; in1.open("input.txt");
ofstream out1; out1.open("output.txt", ofstream::app);
in1>>a>>b;
out1<<a+b<<endl;
return 0;
}
sstream=istringstream+ostringstream
//读写字符串
#include<iostream>
#include<sstream>
using namespace std;
int main(){
string a = "abcde";
istringstream st1; //定义输入流
st1.str(a); //拷贝内容到流中
string b = st1.str();//返回流中内容
string c; st1>>c;//输出内容到流中
ostringstream st2; //定义输出流
st2<<a<<"12345"; //输出内容到流中
string d = st2.str(); //返回流中内容
cout<<b<<" "<<c<<" "<<d<<endl;
return 0;
}
2、输出格式
#include<iostream>
#include<iomanip>//不要忘记包含此头文件
using namespace std;
int main(){
int a;
cout<<"input a:";
cin>>a;
cout<<"dec:"<<dec<<a<<endl; //以十进制形式输出整数
cout<<"hex:"<<hex<<a<<endl; //以十六进制形式输出整数a
cout<<"oct:"<<setbase(8)<<a<<endl; //以八进制形式输出整数a
char *pt="China"; //pt指向字符串"China"
cout<<setw(10)<<pt<<endl; //指定域宽为,输出字符串
cout<<setfill('*')<<setw(10)<<pt<<endl; //指定域宽,输出字符串,空白处以'*'填充
double pi=22.0/7.0; //计算pi值
//按指数形式输出,8位小数
cout<<setiosflags(ios::scientific)<<setprecision(8);
cout<<"pi="<<pi<<endl; //输出pi值
cout<<"pi="<<setprecision(4)<<pi<<endl; //改为位小数
cout<<"pi="<<setiosflags(ios::fixed)<<pi<<endl; //改为小数形式输出
return 0;
}
3、<<重载
>>运算符左侧为流输入对象，右侧为结构对象，返回一个流输入对象。
注意引用符号&
istream& operator>>(istream& in, complex& A){
in >> A.m_real >> A.m_imag;
return in;
}
实现pair，complex类型。
#include <iostream>
using namespace std;
class complex{
public:
complex(double real = 0.0, double imag = 0.0): m_real(real), m_imag(imag){ };
public:
friend complex operator+(const complex & A, const complex & B);
friend complex operator-(const complex & A, const complex & B);
friend complex operator*(const complex & A, const complex & B);
friend complex operator/(const complex & A, const complex & B);
friend istream & operator>>(istream & in, complex & A);
friend ostream & operator<<(ostream & out, complex & A);
private:
double m_real; //实部
double m_imag; //虚部
};
//重载加法运算符
complex operator+(const complex & A, const complex &B){
complex C;
C.m_real = A.m_real + B.m_real;
C.m_imag = A.m_imag + B.m_imag;
return C;
}
//重载减法运算符
complex operator-(const complex & A, const complex &B){
complex C;
C.m_real = A.m_real - B.m_real;
C.m_imag = A.m_imag - B.m_imag;
return C;
}
//重载乘法运算符
complex operator*(const complex & A, const complex &B){
complex C;
C.m_real = A.m_real * B.m_real - A.m_imag * B.m_imag;
C.m_imag = A.m_imag * B.m_real + A.m_real * B.m_imag;
return C;
}
//重载除法运算符
complex operator/(const complex & A, const complex & B){
complex C;
double square = A.m_real * A.m_real + A.m_imag * A.m_imag;
C.m_real = (A.m_real * B.m_real + A.m_imag * B.m_imag)/square;
C.m_imag = (A.m_imag * B.m_real - A.m_real * B.m_imag)/square;
return C;
}
//重载输入运算符
istream& operator>>(istream& in, complex& A){
in >> A.m_real >> A.m_imag;
return in;
}
//重载输出运算符
ostream& operator<<(ostream& out, complex& A){
out << A.m_real <<" + "<< A.m_imag <<" i ";;
return out;
}
int main(){
complex c1, c2, c3;
cin>>c1>>c2;
c3 = c1 + c2;
cout<<"c1 + c2 = "<<c3<<endl;
c3 = c1 - c2;
cout<<"c1 - c2 = "<<c3<<endl;
c3 = c1 * c2;
cout<<"c1 * c2 = "<<c3<<endl;
c3 = c1 / c2;
cout<<"c1 / c2 = "<<c3<<endl;
return 0;
}
文章来源: gwj1314.blog.csdn.net，作者：小哈里，版权归原作者所有，如需转载，请联系作者。
原文链接：gwj1314.blog.csdn.net/article/details/108399266
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