如何从文件中扫描数字到数组? [英] How do I scan in numbers to an array from a file?

问题描述

说我有一个带有数字的文件: 1 2 3 4 5 6 7 8 9 10 -1

Say I have a file with the numbers: 1 2 3 4 5 6 7 8 9 10 -1

我想读入该文件并存储该文件的所有值，并在控制变量-1处停止.

I want to read in that file and store all the values of that file, stopping at the control variable -1.

因此，如果我将该数组打印到另一个文件，它将看起来像: 1 2 3 4 5 6 7 8 9 10

So if I printed that array to another file it would look like: 1 2 3 4 5 6 7 8 9 10

这给了我所有数字，但其中包括-1.我该如何放弃-1?

This gives me all the numbers, but it has -1 included. How can I drop off the -1?

   int arr[100];
   int n;
   while (scanf("%d",&arr[n]) > 0)
       n++;

推荐答案

您不能添加> 0条件:这将给您带来不确定的行为.为了忽略负数，您可以在读取数字后在循环内添加单独的检查，如下所示:

You cannot add the > 0 condition: this would give you undefined behavior. In order to ignore the negative one, you could add a separate check inside the loop, after reading the number, like this:

while (scanf("%d", &arr[n]) != EOF) {
    if (arr[n] > 0) {
        n++;
    }
}

由于数组arr具有固定大小，因此最好防止出现超限，如下所示:

Since the array arr has fixed size, it would be a good idea to guard against overruns, like this:

while (n < 100 && scanf("%d", &arr[n]) != EOF) {
    if (arr[n] > 0) {
        n++;
    }
}

如果文件结束前达到100，此循环将停止.请注意，您还需要在循环之前将n初始化为零，以避免未定义的行为.

This loop would stop if you reach 100 before the file ends. Note that you also need to initialize n to zero before the loop to avoid undefined behavior.

这是关于ideone的演示.

这篇关于如何从文件中扫描数字到数组?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！