如何在 C++ 中逐行读取文件中的整数组
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How to read groups of integers from a file, line by line in C++
提问by Peter Smit
I have a text file with on every line one or more integers, seperated by a space. How can I in an elegant way read this with C++? If I would not care about the lines I could use cin >>, but it matters on which line integers are.
我有一个文本文件，每一行都有一个或多个整数，用空格分隔。我怎样才能用 C++ 以优雅的方式阅读这个？如果我不关心我可以使用 cin >> 的行，但重要的是在哪一行整数上。
Example input:
示例输入：
1213 153 15 155
84 866 89 48
12
12 12 58
12
回答by David Rodríguez - dribeas
It depends on whether you want to do it in a line by line basis or as a full set. For the whole file into a vector of integers:
这取决于您是要逐行还是完整地进行。将整个文件转化为整数向量：
int main() {
std::vector<int> v( std::istream_iterator<int>(std::cin),
std::istream_iterator<int>() );
}
If you want to deal in a line per line basis:
如果您想在每行基础上处理一行：
int main()
{
std::string line;
std::vector< std::vector<int> > all_integers;
while ( getline( std::cin, line ) ) {
std::istringstream is( line );
all_integers.push_back(
std::vector<int>( std::istream_iterator<int>(is),
std::istream_iterator<int>() ) );
}
}
回答by synepis
You could do smtng like this(I used cin, but you can use any other file stream):
您可以像这样执行 smtng（我使用了 cin，但您可以使用任何其他文件流）：
string line;
while( getline( cin, line ) )
{
istringstream iss( line );
int number;
while( iss >> number )
do_smtng_with_number();
}
Or:
或者：
int number;
while( cin >> number )
{
do_smtng_with_number();
}
回答by Jerry Coffin
What result do you want? If you want all the integers in a single vector, you could do something like:
你想要什么结果？如果您想要单个向量中的所有整数，您可以执行以下操作：
std::ifstream input("input.txt");
std::vector<int> data(std::istream_iterator<int>(input),
std::istream_iterator<int>());
That discards the line-structure though -- you end up with the data all together. One easy way to maintain the original line structure is to read a line with getline, initialize a stringstream with that string, then put the values from that stringstream into a vector (and push that onto the back of a vector of vectors of int).
尽管如此，这丢弃了线结构——你最终得到了所有的数据。维护原始行结构的一种简单方法是使用 getline 读取一行，使用该字符串初始化 stringstream，然后将该 stringstream 中的值放入一个向量中（并将其推到 int 向量的向量的后面）。
std::vector<std::vector<int> > data;
std::vector<int> temp;
std::string t;
while (std::getline(input, t)) {
std::istringstream in(t);
std::copy(std::istream_iterator<int>(in),
std::istream_iterator<int>(),
std::back_inserter(temp);
data.push_back(temp);
}
回答by Desai
Here you go :
干得好 ：
void readFromFile(string filename)
{
string line;
ifstream myfile(filename);
if (myfile.is_open())
{
while ( getline(myfile,line) )
{
cout << line << '\n';
}
myfile.close();
}
}
int main(int argc, char* argv)
{
readFromFile("Input.txt");
getchar();
return 0;
}
