如何从文本c ++获得双打 [英] How to get doubles from text c++

问题描述

我有一个文本文档，看起来像这样：

  user_name1 1.575 
 user_name2 3.636 
 user_name3 2.647 
 user_name4 5.532 
 user_name5 4.253 
  

我要做的是，将这些数字从.txt文件获取到控制台并将它们保存为变量。我知道如何读取.txt文件在控制台，我发现一些答案在这里如何获得每行单独作为字符串，但我不能得到这些双打。

我试过这个：

1）获取每行的字符串
2）循环遍历它们并检查ASCII码，如果它是一个数字，我保存下3或4个字符

但是它的工作不是很好。非常感谢您的帮助。

 
   string line; 
 
 ifstream banka（banka.txt）; 
 
 double numbers [5]; 
 if（banka.is_open（））{
 for（int i = 0; i <5; i ++）{
 getline（cin，line）; 
 size_t space = line.find（''）; 
 string numStr = line.substr（space + 1）; 
 double num = stod（numStr）; 
 numbers [i] = num; 
 
} 
 banka.close（）; 
} 
 else {
 cout<<无法打开文件。<< endl; 
} 
  

解决方案

  std :: string ln; // line 
 while（std :: getline（std :: cin，ln））{
 std :: size_t space = ln.find（''）; 
 std :: string nameStr = ln.substr（0，space）; 
 std :: string numStr = ln.substr（space + 1）; 
 double num = std :: stod（numStr）; 
} 
  

I have a text document which looks something like this:

user_name1 1.575
user_name2 3.636
user_name3 2.647
user_name4 5.532
user_name5 4.253

What i am trying to do is, to get these numbers from .txt file into console and save them as variables. I know how to read .txt file in console and I found some answers here how to get each line separately as strings, but i can't get these doubles. Is there some kind of function or whatsoever that goes through strings and finds numbers?

I tried with this:

1) get string of each line 2) loop through them and check ASCII code and if it is a number I saved next 3 or 4 charachters

But its not working very well. Thanks for your help in advance.

EDIT:

string line;

ifstream banka ("banka.txt");

double numbers[5];
if(banka.is_open()) {
    for(int i=0; i<5; i++) {
        getline(cin,line);
        size_t space=line.find(' ');
        string numStr=line.substr(space+1);
        double num = stod(numStr);
        numbers[i]=num;

    }
    banka.close();
}
else {
    cout<<"Unable to open file."<<endl;
}

解决方案

This:

std::string ln; // line
while (std::getline(std::cin, ln)) {
    std::size_t space = ln.find(' ');
    std::string nameStr = ln.substr(0, space);
    std::string numStr = ln.substr(space + 1);
    double num = std::stod(numStr);
}

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