如何在C ++中将文件读入向量？ [英] How to read a file into vector in C++?

问题描述

我需要读取 .data 或 .txt 文件，其中包含新的将每行的浮点数编号到一个向量中。

我已经搜索了很多并且应用了许多不同的方法，但是每次得到相同的结果， Main.size（） code> 0 和一个错误说矢量下标超出范围，所以显然这个矢量是只是没有读取任何文件。
$ b

注意：文件既在文件夹中也包含在VS项目中。

无论如何，这里是我的代码：

  #include< iostream> 
 #include< fstream> 
 #include< sstream> 
 #include< vector> 
 #include< string> 
 
使用namespace std; 
 
 int main（）{
 
 vector< double>主要; 
 int count; 
 string lineData; 
 double tmp; 
 
 ifstream myfile（test.data，ios :: in）; 
 
双数; 
 
 myfile>>计数; 
 for（int i = 0; i< count; i ++）{
 myfile>> TMP; 
 Main.push_back（tmp）; 
 cout<<计数; 
} 
 
 cout<< 编号：\\\
; 
 cout<< Main.size（）; （int i = 0; i =（（Main.size（）） -  1）; i ++）{
 cout< Main [i] << \\\
; 
} 
 
 cin.get（）; 
返回0; 
 
 $ / code $ / pre 
 $ b $ p我得到的结果总是简单的：
 
 
 编号：
 0 
  
 
 
  for（int i = 0; i = 0）解决方案
   

试试这个：

  for（int i = 0; i< Main.size（）; i ++）{
  

另外，将数字读入向量并将其写入标准输出的更习惯方式是沿着这些线的：



  #include< iostream> 
 #include< iterator> 
 #include< fstream> 
 #include< vector> 
 #include< algorithm> //为std :: copy 
 
 int main（）
 {
 std :: ifstream is（numbers.txt）; 
 std :: istream_iterator< double>开始（是），结束; 
 std :: vector< double>数字（开始，结束）; 
 std :: cout<< 阅读<< numbers.size（）<< 数字<<的std :: ENDL; 
 
 //将数字打印到标准输出
 std :: cout<< 数字读入：\ n; 
 std :: copy（numbers.begin（），numbers.end（），
 std :: ostream_iterator< double>（std :: cout，））; 
 std :: cout<<的std :: ENDL; 
 
 
 
 
 
 
 
尽管你应该检查 ifstream 读取错误。
 
I need to read from a .data or .txt file containing a new float number on each line into a vector. 

I have searched far and wide and applied numerous different methods but every time I get the same result, of a Main.size() of 0 and an error saying "Vector Subscript out of Range", so evidently the vector is just not reading anything into the file.

Note: the file is both in the folder and also included in the VS project.

Anyway, here's my code:
#include <iostream>
#include <fstream>
#include <sstream>
#include <vector>
#include <string>

using namespace std;

int main() {

    vector<double> Main;
    int count;
    string lineData;
    double tmp;

    ifstream myfile ("test.data", ios::in);

    double number;  

    myfile >> count;
    for(int i = 0; i < count; i++) {
        myfile >> tmp;
        Main.push_back(tmp);
        cout << count;
    }

    cout << "Numbers:\n";
    cout << Main.size();
    for (int i=0; i=((Main.size())-1); i++) {
        cout << Main[i] << '\n';
    }

    cin.get(); 
    return 0;
}
The result I get is always simply:
Numbers:
0

解决方案
Your loop is wrong:
for (int i=0; i=((Main.size())-1); i++) {
Try this:
for (int i=0; i < Main.size(); i++) {
Also, a more idiomatic way of reading numbers into a vector and writing them to stdout is something along these lines:
#include <iostream>
#include <iterator>
#include <fstream>
#include <vector>
#include <algorithm> // for std::copy

int main()
{
  std::ifstream is("numbers.txt");
  std::istream_iterator<double> start(is), end;
  std::vector<double> numbers(start, end);
  std::cout << "Read " << numbers.size() << " numbers" << std::endl;

  // print the numbers to stdout
  std::cout << "numbers read in:\n";
  std::copy(numbers.begin(), numbers.end(), 
            std::ostream_iterator<double>(std::cout, " "));
  std::cout << std::endl;

}
although you should check the status of the ifstream for read errors.

                        
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