C ++ - 从文件读取到双 [英] C++ - Read from file to double

问题描述

我现在相对来说是编程和学习C ++的课程。我到目前为止没有任何重大问题。我正在做一个程序，其中X数量判断可以得分0.0 - 10.0（双），然后删除最高和最低的一个，然后计算并打印出平均值。

I'm relatively new to programming and taking a course in C++ currently. I haven't had any major problems so far. I am making a program where an X amount judges can score 0.0 - 10.0 (double) and then the highest and lowest one is removed then an average is calculated and printed out.

这部分完成，现在我想从一个文件中读取形状：
example.txt -
10.0
9.5
6.4
3.4
7.5

This part is done, now I want to read from a file in the shape of: example.txt - 10.0 9.5 6.4 3.4 7.5

但我偶然发现了点（。）的问题，以及如何解决这个问题。任何建议和（好的）解释，以便我能理解它？

But I am stumbling onto problems with the dot (.) and how to get around it to get the number into a double. Any suggestions and (good) explanations so I can understand it?

TL; DR：

推荐答案

由于您的文本文件是空格分隔，可以通过使用默认跳过空格的 std :: istream 对象来使用它（在这种情况下， std :: fstream ）：

Since your textfile is whitespace delimited, you can use that to your advantage by utilizing std::istream objects who skip whitespace by default (in this case, std::fstream):

#include <fstream>
#include <vector>
#include <cstdlib>
#include <iostream>

int main() {
    std::ifstream ifile("example.txt", std::ios::in);
    std::vector<double> scores;

    //check to see that the file was opened correctly:
    if (!ifile.is_open()) {
        std::cerr << "There was a problem opening the input file!\n";
        exit(1);//exit or do additional error checking
    }

    double num = 0.0;
    //keep storing values from the text file so long as data exists:
    while (ifile >> num) {
        scores.push_back(num);
    }

    //verify that the scores were stored correctly:
    for (int i = 0; i < scores.size(); ++i) {
        std::cout << scores[i] << std::endl;
    }

    return 0;
}

注意：

强烈建议使用向量代替动态数组，尽可能使用大量的原因：

It is highly recommended to use vectors in lieu of dynamic arrays where possible for a myriad number of reasons as discussed here:

何时使用向量和何时使用使用C ++中的数组？

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