这段代码无法运行，原来以为是路径的问题，把文件删了也进不去

Question

#include <iostream>
#include <cctype>
#include <string>
#include <fstream>

char* functionC(char* destination, const char* source)
{
	int k = 0;
	for (int i = 0; source[i] != '\0'; i++)
	{
		if (!isdigit(source[i])) //isDigit проверяет число ли
		{
			destination[k] = source[i];
			k++;
		}
	}
	destination[k] = '\0';
	return destination;
}

std::string functionString(const std::string& source)
{
	std::string destination = ""; //строка для вывода输出线，输出线
	for (int i = 0; i < source.size(); i++)
	{
		if (!isdigit(source[i]))
		{
			destination += source[i];
		}
	}
	return destination;
}

int main()
{

	std::ifstream infile;
	std::ofstream outfile;

	infile.open("");
	outfile.open("");

	if (infile.peek() == std::ifstream::traits_type::eof()) //проверка на пустой файл空文件检验
	{
		outfile << "File is emrty!\n";
		return 1;
	}
	int length; //длина строки长字符串
	infile >> length;
	while (!infile.eof())
	{
		length++; // учитываем символ \0考虑到符号
		if (infile.fail() || length <= 0)
		{
			outfile << "Invalid string length\n";
			return 1;
		}
		char* arrayC1 = new char[length];
		char* arrayC2 = new char[length];
		arrayC2[0] = '\0';
		infile.ignore(length, '\n');
		infile.get(arrayC1, length);
		for (int i = 0; i < length - 1; i++)
		{
			if (arrayC1[i] == '\0')
			{
				outfile << "Invalid string length\n";
				return 1;
			}
		}
		std::string str = arrayC1;
		outfile << "Source string\t\t\t\t" << str << '\n';
		outfile << "With C-style strings:\t" << functionC(arrayC2, arrayC1) << '\n';
		outfile << "Using the string class:\t" << functionString(str) << '\n';
		delete[] arrayC1;
		delete[] arrayC2;
		infile >> length;
	}
	infile.close();
	outfile.close();
	return 0;
}

Answer 1

一般用

if (infile.fail()) {
    cout << "Failed to open file!"<<endl;
    return 1;
}