读取浮点数到数组中 [英] Reading floats into an array

问题描述

我怎么读10个浮点数并将它们存储在一个数组中而又不浪费任何内存?

How could I read let's say 10 floats and store them in an array without wasting any memory?

推荐答案

啊哈.问题不是读取浮点数，而是内存.您读了 i ，并且需要一个完全容纳 i 浮点数的数组.

Aha. It's not reading the floats that's the problem, it's the memory. You read in i, and you need an array that holds exactly i floats.

这确实闻起来像家庭作业，很好，但是我老师太多了，无法给您完整的答案.因此，我告诉您，您需要的是一个名为 malloc()的C函数和一个名为 sizeof .

This really does smell like homework, which is fine, but I'm too much the teacher to give you the full answer. So I'll tell you, what you need is a C function named malloc() and a C operator (it looks like a function but it's actually built into the language) named sizeof.

请参阅本教程.

是的，你到了那里.这是您注释中的代码，格式设置.

Yup, you got it there. Here's the code from your comment, formatted.

int n,index;
float temp;
scanf("%d",&n);
float *pValues=(float *)calloc(n,sizeof(float));
for(index=0;index<n;index++) {
    scanf("%f",&temp); 
    *(pValues+index)=temp;
}

我要做两个更改:

1. 将malloc用于字符之外的其他任何东西
2. 在C语言中，数组和指针之间的关系非常密切；实际上，*(pValues+index)完全等同于pValues[index].

1. Its more idiomatic to use malloc for anything besides characters
2. In C, arrays and pointers have a very close relationship; in fact *(pValues+index) is exactly equivalent to pValues[index].

所以我将其重写为:

int n,index;
float temp;
scanf("%d",&n);
float *pValues=(float *)malloc(n*sizeof(float));
for(index=0;index<n;index++) {
    scanf("%f",&temp); 
    pValues[index]=temp;
}

让我们看一下代码的另一种转换.您有pValues，它是指向float的指针.您有&temp，它也是float的指针，因为&是运算符的地址，而temp是float. AND，您只是对索引进行指针算术运算.因此，我们可以再重写一次为:

Let's look at one more transformation of the code. You have pValues, which is a pointer to float. You have &temp, which is also a pointer to float, because & is the address-of operator and temp is a float. AND, you're just doing pointer arithmetic with your index. So, we could rewrite this one more time as:

int n,index;    // Don't need temp
scanf("%d",&n);
float *pValues=(float *)malloc(n*sizeof(float));
for(index=0;index<n;index++) {
    scanf("%f",pValues+index); 
}

现在，测验问题:如果执行循环，会发生什么

Now, quiz question: what would happen if you made the loop

for(index=0;index<n;index++) {
    scanf("%f",pValues++); 
}

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