C++

1.1、C++中substr函数用法_获取文件名的一部分

//1.1、C++中substr函数用法_获取文件名的一部分

#include
#include
using namespace std;

string s = "E:Copy_data_20220217aaaaaa.MP4";

int main()
{
	
	//string a = s.substr(0, 5); //获得字符串s中从第0位开始的长度为5的字符串
	std::size_t last_pos = s.find_last_of(".");
	std::string a = s.substr(0, last_pos);
	std::string vid_format = s.substr(last_pos + 1);
	cout << a << endl;
	cout << vid_format << endl;
	system("Pause");		//按任意键后退出
	return 0;
}

1.2、获取文件名的前缀和后缀

//1.2、获取文件名的前缀和后缀

#include 
#include 

using namespace std;

int main()
{
	string name1 = "/a/b/c/v/zhiodfh.jpg";
	int pos1 = name1.find_last_of('/');
	string name2 = name1.substr(pos1 + 1);
	cout << "pos1:" << pos1 << endl;
	cout << "name2:" << name2 << endl;
	int pos2 = name2.find('.');
	string name3 = name2.substr(0, pos2);
	cout << "name3:" << name3 << endl;
	system("Pause");		//按任意键后退出
	return 0;
}

2、20220401_C++ txt文件的读操作

//2、20220401_C++ txt文件的读操作


#include 
#include 
#include 
#include 

using namespace std;
void writeTxt(string file);
void readTxt(string file);

string filename = "C:\Users\Administrator\Desktop\ceshi\videos.txt";

int main()
{
	writeTxt(filename);
	readTxt(filename);
	system("Pause");		//按任意键后退出
}

void writeTxt(string file)	//写入hello world
{
	ofstream outfile;
	outfile.open(file.data());   //将文件流对象与文件连接起来 
	assert(outfile.is_open());   //若失败,则输出错误消息,并终止程序运行 

	outfile << "hello," << endl << "world." << endl;
	outfile.close();

}

void readTxt(string file)	//读出hello world
{
	ifstream infile;
	infile.open(file.data());   //将文件流对象与文件连接起来 
	assert(infile.is_open());   //若失败,则输出错误消息,并终止程序运行 

	string s;			//逐行输出txt文本中的内容
	while (getline(infile, s))
	{
		cout << s << endl;
	}
	infile.close();             //关闭文件输入流 

}

3、20220402读文件夹下文件名（各类文件的文件名），写入txt_可用

//3、20220402读文件夹下文件名（各类文件的文件名），写入txt_可用

#include
#include
#include
#include 
#include 

using namespace std;
//void getFiles(string path, vector& files);
void getFiles(string, vector&);		//得到文件夹下所有的文件名

string filefolder = "E:\Copy_data_20220217";
string filename = "C:\Users\Administrator\Desktop\vid.txt";


int main()
{
	vector files;
	getFiles(filefolder, files);

	ofstream outdata;
	for (int j = 0; j < files.size(); ++j)
	{
		cout << files[j] << endl;
		outdata.open(filename, ios::app);		//打开文件txt文件，ios::app是尾部追加的意思
		//outdata << files[j] << endl;              //把文件夹下的文件名写入到txt中
		outdata << "1" << "_" << files[j] << endl;
		outdata.close();					//关闭文件
	}
	system("Pause");		//按任意键后退出
	return 0;
}

void getFiles(string path, vector& files)
{
	intptr_t hFile = 0;		//文件句柄
	struct _finddata_t fileinfo;		//文件信息
	string p;

	if ((hFile = _findfirst(p.assign(path).append("\*").c_str(), &fileinfo)) != -1)
	{
		do
		{
			//如果是目录,迭代之
			//如果不是,加入列表
			if ((fileinfo.attrib &  _A_SUBDIR))
			{
				if (strcmp(fileinfo.name, ".") != 0 && strcmp(fileinfo.name, "..") != 0)
					getFiles(p.assign(path).append("\").append(fileinfo.name), files);
			}
			else
			{
				files.push_back(p.assign(path).append("\").append(fileinfo.name));
			}
		} while (_findnext(hFile, &fileinfo) == 0);
		_findclose(hFile);
	}
}

4.1、vector_一维数据输入，找出一对石头

//4.1、vector_一维数据输入，找出一对石头

#include
#include
using namespace std;

int main()
{
	int N,we;	//N是石头个数，we是石头权值
	int temp;	//temp暂存某一权值的变量
	int M=0;	//权值不同的石头序号组数
	cout << "请输入石头个数：";
	cin >> N;
	vector array(N);//声明变长数组

	//输入所有石头的权值
	for (int i = 0; i < N; i++)
	{
		cout << "请输入"<> we;
		array[i] = we;
	}

	//显示石头序号及对应权值
	cout << "石头数为"< 
4.2、vector_二维数据的输入和显示
 
//4.2、vector_二维数据的输入和显示


#include 
#include 
using namespace std;

int main()
{
	int num1,//行数
		num2;//列数

	cout << "Please enter the number for row and column: " << endl;
	cin >> num1 >> num2;

	//为二维数组开辟空间
	int **p = new int*[num1];
	for (int i = 0; i < num1; ++i)
		p[i] = new int[num2];

	for (int j = 0; j < num1; j++)
	{
		for (int k = 0; k < num2; k++)
		{
			p[j][k] = (j + 1)*(k + 1);
			cout << setw(6) << p[j][k] << ':' << setw(8) << &p[j][k];
		}
		cout << endl;
	}

	//释放二维数组占用的空间
	for (int m = 0; m < num1; m++)
		delete[] p[m];
	delete[] p;

	return 0;
}
 
5.1、C++继承实例
 
//5.1、C++继承实例


#include
#include
#include
using namespace std;

class parent
{
protected:
	string pname;
public:
	parent(string name)
	{
		pname = name;
	}
	virtual void printname() {};
};

class child :public parent
{
protected:
	string cname;
public:
	child(string name):parent(name)
	{
		cname = name;
	}
	virtual void printname()
	{
		cout << "this is child,cname is" << cname << ",pname is" << pname << endl;
	}
};


class grandchild :public child
{
private:
	string gname;
public:
	grandchild(string name) :child(name)
	{
		gname = name;
	}
	virtual void printname()
	{
		cout << "this is grandchild,gname is" << gname << ", cname is" << cname << ",pname is" << pname << endl;
	}
};


int main()
{
	string name = "C";
	child Child(name);
	name = "GC";
	grandchild Gchild(name);

	vector mlist;
	mlist.push_back(dynamic_cast(&Child));
	mlist.push_back(dynamic_cast(&Gchild));

	for (int i = 0; i < mlist.size(); i++)
		mlist[i]->printname();
	return 0;
}

 
5.2、C++多态示例代码
 
//5.2、C++多态示例代码


#include
using namespace std;

class A
{
public:
	virtual void disp(int n)
	{
		cout << "A::disp n=" << n << endl;
	}
};

class B :public A
{
public:
	virtual void disp(double m)
	{
		cout << "B::disp m=" << m << endl;
	}
};

void fn(A &a)
{
	a.disp(5.5);
}

int main()
{
	B b;
	fn(b);
	return 0;
}

 
5.3、C++封装
 
//5.3、C++封装

#include
using namespace std;
const double PI = 3.14;
class Circle
{
public:
	int m_r;
	double calculateZC()
	{
		return 2 * PI*m_r;
	}
};

int main()
{
	Circle c1;
	c1.m_r = 10;
	cout << "圆的周长为：" << c1.calculateZC() << endl;
	system("pause");
	return 0;
}

 
6.1修改txt中某一行的数据，并保存在某一行（整行替换）
 
//6.1修改txt中某一行的数据，并保存在某一行（整行替换）




#include 
#include 
#include 
#include 

using namespace std;

void ModifyLineData(char*, int, char*);

void main()
{
	ModifyLineData("C:\Users\Administrator\Desktop\vid.txt", 3, "0");
	system("Pause");		//按任意键后退出

}

void ModifyLineData(char* fileName, int lineNum, char* lineData)
{
	ifstream in;
	in.open(fileName);
	string strFileData = "";
	int line = 1;
	char tmpLineData[1024] = { 0 };
	while (in.getline(tmpLineData, sizeof(tmpLineData)))
	{
		if (line == lineNum)
		{
			//cout << strFileData << endl;
			strFileData += string(lineData);
			strFileData += "n";
		}
		else
		{
			strFileData += string(tmpLineData);
			strFileData += "n";
		}
		line++;
	}
	in.close();
	//写入文件
	ofstream out;
	out.open(fileName);
	out.flush();
	out << strFileData;
	out.close();
}

 
6.2修改txt中某一行中指定位置的数据，并保存在某一行
 
//6.2修改txt中某一行中指定位置的数据，并保存在某一行




#include 
#include 
#include 
#include 

using namespace std;

void ModifyLineData(char* , int , char* );

void main()
{
	ModifyLineData("C:\Users\Administrator\Desktop\vid.txt", 4, "0");
	system("Pause");		//按任意键后退出
	
}

void ModifyLineData(char* fileName, int lineNum, char* lineData)
{
	ifstream in;
	in.open(fileName);
	string strFileData = "";
	int line = 1;
	char tmpLineData[1024] = { 0 };
	while (in.getline(tmpLineData, sizeof(tmpLineData)))
	{
		
		int pos1 = string(tmpLineData).find_first_of('_');
		string first = string(tmpLineData).substr(0, pos1);
		string leftover = string(tmpLineData).substr(pos1 + 1);

		bool format_ind = (first == "1");
		if (format_ind)
		{
			string temp1 = string(lineData) + string("_") + string(leftover);
			strFileData += temp1;
			strFileData += "n";

		}
		else
		{
			continue;
		}

		line++;
	}
	in.close();
	//写入文件
	ofstream out;
	out.open(fileName);
	out.flush();
	out << strFileData;
	out.close();
}

 
7、复制txt内容到另外一个txt
 
//7、复制txt内容到另外一个txt



#include 
#include  
using namespace std;

void copyTXT(string, string);

string filename = "C:\Users\Administrator\Desktop\vid.txt";
string filename1 = "C:\Users\Administrator\Desktop\videos.txt";

int main() 
{

	copyTXT(filename, filename1);

	return 0;
}

void copyTXT(string filename, string filename1)
{
	ifstream infile(filename);
	ofstream outfile(filename1, ios::app);

	char c;
	while (infile.get(c))
	{
		outfile << c;
	}

	infile.close();
	outfile.close();
}

 
8、创建文件夹
 
//8、创建文件夹



#include 
using namespace std;

int main()
{
	string folderPath = "C:\Users\Administrator\Desktop\123";

	string command = "mkdir " + folderPath;
	system(command.c_str());

	system("Pause");		//按任意键后退出
	return 0;
}

 
9、创建C++文件夹以及C++文件名的提取
 
//9、创建C++文件夹以及C++文件名的提取



#include 
#include 

using namespace std;

int main()
{
	char p[50];
	//string video_name_all = "1_E:Copy_data_20220217aaaa.MP4";
	

	string video_name_all = "1_E:\Copy_data_20220217\aaaa.MP4";

	std::size_t pos = video_name_all.find_last_of("\");

	std::size_t pos1 = video_name_all.find(".");

	std::string video_name = video_name_all.substr(pos+1);

	std::cout << video_name << std::endl;

	

	system("Pause");		//按任意键后退出
	return 0;
}

 
10、从完整路径中提取文件名、不带后缀的名字、后缀名
 
//10、从完整路径中提取文件名、不带后缀的名字、后缀名



#include  
#include 
using namespace std;
void main()
{
	string path = "C:\Users\Administrator\Desktop\text\data.22.txt";

	//1.获取不带路径的文件名
	string::size_type iPos = path.find_last_of('\') + 1;
	string filename = path.substr(iPos, path.length() - iPos);
	cout << filename << endl;

	//2.获取不带后缀的文件名
	string name = filename.substr(0, filename.rfind("."));
	cout << name << endl;

	//3.获取后缀名
	string suffix_str = filename.substr(filename.find_last_of('.') + 1);
	cout << suffix_str << endl;

	system("Pause");		//按任意键后退出
}

 
11、修改txt中的内容，写入到另一个txt文件中
 
//11、修改txt中的内容，写入到另一个txt文件中



#include 
#include 
#include 

using namespace std;

int main()
{
	ifstream in("C:\Users\Administrator\Desktop\20220428\test.txt");
	ofstream out("C:\Users\Administrator\Desktop\20220428\rec_gt_test.txt");
	string filename;
	string line;

	if (in) // 有该文件
	{
		while (getline(in, line)) // line中不包括每行的换行符
		{
			//int pos1 = string(line).find_last_of('/');
			//string leftover = string(line).substr(pos1 + 1);
			//cout << leftover << endl;
			//out << leftover << endl; // 输入到2.txt中
			string temp = "test/";
			cout << line << endl;
			out << temp << line << endl; // 输入到2.txt中
		}
	}
	else // 没有该文件
	{
		cout << "no such file" << endl;
	}

	return 0;
}