C++ 从字符串中拆分 int
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原文地址: http://stackoverflow.com/questions/3421817/
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splitting int from a string
提问by brett
I have string with number on ints seperated by space delimiter. Can some one help me how to split the string into ints. I tried to use find and then substr. Is there a better way to do it ?
我在整数上有由空格分隔符分隔的数字字符串。有人可以帮助我如何将字符串拆分为整数。我尝试使用 find 然后使用 substr。有没有更好的方法来做到这一点？
回答by
Use a stringsteam:
使用串串：
#include <string>
#include <sstream>
int main() {
std::string s = "100 123 42";
std::istringstream is( s );
int n;
while( is >> n ) {
// do something with n
}
}
回答by Kisalay
This has been discussed as part of Split a string in C++?
Also, you can use boost library split function to achieve the splitting without a loop in your program. Eg.
此外，您可以使用boost库拆分功能来实现程序中没有循环的拆分。例如。
boost::split(epoch_vector, epoch_string, boost::is_any_of(","));
boost::split(epoch_vector, epoch_string, boost::is_any_of(","));
回答by Brian O'Kennedy
A version using boost. The stringstream version from Neil is so much simpler!
使用 boost 的版本。Neil 的 stringstream 版本要简单得多！
#include <iostream>
#include <vector>
#include <algorithm>
#include <boost/lexical_cast.hpp>
#include <boost/tokenizer.hpp>
int main()
{
const std::string str( "20 30 40 50" );
std::vector<int> numbers;
boost::tokenizer<> tok(str);
std::transform( tok.begin(), tok.end(), std::back_inserter(numbers),
&boost::lexical_cast<int,std::string> );
// print them
std::copy( numbers.begin(), numbers.end(), std::ostream_iterator<int>(std::cout,"\n") );
}
回答by RiGonz
I had some trouble when reading and converting more than one string (I found I had to clear the string stream). Here a test I made with multiple int/string conversions with read/write to an i/o file.
我在读取和转换多个字符串时遇到了一些麻烦（我发现我必须清除字符串流）。这是我使用多个 int/string 转换进行的测试，读取/写入 i/o 文件。
#include <iostream>
#include <fstream> // for the file i/o
#include <string> // for the string class work
#include <sstream> // for the string stream class work
using namespace std;
int main(int argc, char *argv[])
{
// Aux variables:
int aData[3];
string sData;
stringstream ss;
// Creation of the i/o file:
// ...
// Check for file open correctly:
// ...
// Write initial data on file:
for (unsigned i=0; i<6; ++i)
{
aData[0] = 1*i;
aData[1] = 2*i;
aData[2] = 3*i;
ss.str(""); // Empty the string stream
ss.clear();
ss << aData[0] << ' ' << aData[1] << ' ' << aData[2];
sData = ss.str(); // number-to-string conversion done
my_file << sData << endl;
}
// Simultaneous read and write:
for (unsigned i=0; i<6; ++i)
{
// Read string line from the file:
my_file.seekg(0, ios::beg);
getline (my_file, sData); // reads from start of file
// Convert data:
ss.str(""); // Empty the string stream
ss.clear();
ss << sData;
for (unsigned j = 0; j<3; ++j)
if (ss >> aData[j]) // string-to-num conversion done
;
// Write data to file:
my_file.seekp(0, ios::end);
my_file << 100+aData[0] << ' '; // appends at the end of stream.
my_file << 100+aData[1] << ' ';
my_file << 100+aData[2] << endl;
}
// R/W complete.
// End work on file:
my_file.close();
cout << "Bye, world! \n";
return 0;
}
