有没有办法重新排列文本文件中的数字 [英] is there a way to rearrange numbers inside a text file

问题描述

在一个名为numbers.txt的文本文件中说我有5个数字

10

11

14

1

100



我可以随意重新排列它们，这样当我打开numbers.txt

有一个新的随机数字顺序？

say in a text file called numbers.txt i have 5 numbers
10
11
14
1
100

is there a way that I can rearrange them randomly so that when I open numbers.txt
there is a new random order of the numbers?

推荐答案

没有标准（甚至简单）的方法：这是唯一的方法是将整个文件读入内存，随机重新排序，然后写一个全新的文件。



问题是你的线路不一样长度，因此您不能进行行内数据的文件内交换，因为它不会始终保持行正确。文本文件并不真正了解行 - 只是行终止符 - 所以为了在第一行添加或删除单个字符，你必须将整个文件重写为一个字符！

There is no standard (or even simple) way to do that: the only way to do this is to read the entire file into memory, randomly re-order them, and write a whole new file.

The problem is that your lines aren't all the same length, so you can't do "in-file" swapping of line data because it won't always leave the lines correct. Text files don't really know about lines - just line terminator characters - so in order to add or remove a single character to / from the first line you have to rewrite the entire file one character out of place!

根据建议，您必须读取所有数字，将它们重新排列在内存中，然后将它们写回原始文件（覆盖它）。 Modern C ++使任务简洁（参见C ++ 11 Stream Iterators感觉像Python [ ^ ]）

As suggested, you have to read all the numbers, rearrange them in memory and then write back them on the original file (overwriting it). Modern C++ makes the task concise (see "C++11 Stream Iterators feel like Python"[^])

#include <iterator>
#include <string>
#include <fstream>
#include <vector>
#include <algorithm>
using namespace std;

int main()
{
    ifstream ifs("in.txt");
    istream_iterator< int > ii ( ifs );
    istream_iterator< int > iie;
    vector < int > v ( ii, iie);
    ifs.close();
    ofstream ofs("out.txt");
    random_shuffle( v.begin(), v.end() );
    copy( v.begin(), v.end(), ostream_iterator <int> ( ofs, "\n") );
}

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