[英]Reading line from text file and putting the strings into a vector?
我正在嘗試讀取文本文件的每一行,每行包含一個單詞並將這些單詞放入一個向量中。 我該怎么做?
這是我的新代碼:我認為它仍然有問題。
#include <iostream>
#include <fstream>
#include <string>
#include <vector>
using namespace std;
int main()
{
std::string line;
vector<string> DataArray;
vector<string> QueryArray;
ifstream myfile("OHenry.txt");
ifstream qfile("queries.txt");
if(!myfile) //Always test the file open.
{
cout<<"Error opening output file"<<endl;
system("pause");
return -1;
}
while (std::getline(qfile, line))
{
QueryArray.push_back(line);
}
if(!qfile) //Always test the file open.
{
cout<<"Error opening output file"<<endl;
system("pause");
return -1;
}
while (std::getline(qfile, line))
{
QueryArray.push_back(line);
}
cout<<QueryArray[0]<<endl;
cout<<DataArray[0]<<endl;
}
@FailedDev 確實列出了最簡單的形式。 作為替代方案,以下是我經常編碼該循環的方式:
std::vector<std::string> myLines;
std::copy(std::istream_iterator<std::string>(myfile),
std::istream_iterator<std::string>(),
std::back_inserter(myLines));
整個程序可能如下所示:
// Avoid "using namespace std;" at all costs. Prefer typing out "std::"
// in front of each identifier, but "using std::NAME" isn't (very) dangerous.
#include <iostream>
using std::cout;
using std::cin;
#include <fstream>
using std::ifstream;
#include <string>
using std::string;
#include <vector>
using std::vector;
#include <iterator>
using std::istream_iterator;
#include <algorithm>
using std::copy;
int main()
{
// Store the words from the two files into these two vectors
vector<string> DataArray;
vector<string> QueryArray;
// Create two input streams, opening the named files in the process.
// You only need to check for failure if you want to distinguish
// between "no file" and "empty file". In this example, the two
// situations are equivalent.
ifstream myfile("OHenry.txt");
ifstream qfile("queries.txt");
// std::copy(InputIt first, InputIt last, OutputIt out) copies all
// of the data in the range [first, last) to the output iterator "out"
// istream_iterator() is an input iterator that reads items from the
// named file stream
// back_inserter() returns an interator that performs "push_back"
// on the named vector.
copy(istream_iterator<string>(myfile),
istream_iterator<string>(),
back_inserter(DataArray));
copy(istream_iterator<string>(qfile),
istream_iterator<string>(),
back_inserter(QueryArray));
try {
// use ".at()" and catch the resulting exception if there is any
// chance that the index is bogus. Since we are reading external files,
// there is every chance that the index is bogus.
cout<<QueryArray.at(20)<<"\n";
cout<<DataArray.at(12)<<"\n";
} catch(...) {
// deal with error here. Maybe:
// the input file doesn't exist
// the ifstream creation failed for some other reason
// the string reads didn't work
cout << "Data Unavailable\n";
}
}
最簡單的形式:
std::string line;
std::vector<std::string> myLines;
while (std::getline(myfile, line))
{
myLines.push_back(line);
}
不需要瘋狂的c東西:)
編輯:
#include <iostream>
#include <fstream>
#include <string>
#include <vector>
int main()
{
std::string line;
std::vector<std::string> DataArray;
std::vector<std::string> QueryArray;
std::ifstream myfile("OHenry.txt");
std::ifstream qfile("queries.txt");
if(!myfile) //Always test the file open.
{
std::cout<<"Error opening output file"<< std::endl;
system("pause");
return -1;
}
while (std::getline(myfile, line))
{
DataArray.push_back(line);
}
if(!qfile) //Always test the file open.
{
std::cout<<"Error opening output file"<<std::endl;
system("pause");
return -1;
}
while (std::getline(qfile, line))
{
QueryArray.push_back(line);
}
std::cout<<QueryArray[20]<<std::endl;
std::cout<<DataArray[12]<<std::endl;
return 0;
}
使用關鍵字是非法的 C++! 永遠不要使用它。 好的? 好的。 現在比較我寫的和你寫的,並嘗試找出不同之處。 如果您還有問題,請回來。
最簡單的版本:
std::vector<std::string> lines;
for (std::string line; std::getline( ifs, line ); /**/ )
lines.push_back( line );
我省略了包括和其他垃圾。 我的版本與 FailedDev 的版本幾乎相同,但是通過使用“for”循環,我將“line”的聲明放入循環中。 這不僅僅是減少行數的技巧。 這樣做會減少行的范圍——它在 for 循環后消失。 所有變量都應該具有盡可能小的作用域,因此這樣更好。 For 循環很棒。
C++11 及更高版本的簡短版本。 該向量直接從文件內容構建:
ifstream qfile("queries.txt");
vector<string> lines {
istream_iterator<string>(qfile),
istream_iterator<string>()
};
請注意,此代碼僅在輸入文件采用 OP 描述的格式時才有效,即“每行包含一個單詞”。 或者,如果您通過 qfile.imbue() 設置特殊語言環境,正如 mheyman 所指出的那樣。
聲明:本站的技術帖子網頁,遵循CC BY-SA 4.0協議,如果您需要轉載,請注明本站網址或者原文地址。任何問題請咨詢:yoyou2525@163.com.