在使用数组的for循环 - C ++ [英] Using an array in a for loop - C++

问题描述

我想设置一个测试条件，以确定数组的大小，然后通过在为循环数组中的每个值移动。

I want to set a test condition to determine the size of an array, and then move through each value of the array in a for loop.

拿这个数组例如：

std::string expenses[] = {"housing", "utilities", "household expenses", "transportation", "food", "medical", "insurance", "entertainment", "clothing", "misc"};  

的括号是空的，里面还有10个元素。你会如何​​创建这样的为循环，而无需创建持有的10一个int一个独立的变量？

The brackets are empty, and there are 10 elements in there. How would you create a for loop for this without creating a separate variable that holds an int of 10?

推荐答案

如果你的意思是通过每个元素运行（相同的范围），那么黑暗是正确的：

If you mean to run through each element (within the same scope), then 'The Dark' is correct:

#include <string>
#include <iostream> 

int main()
{
  std::string expenses[] = {"housing", "utilities", "household expenses", "transportation", "food", "medical", "insurance", "entertainment", "clothing", "misc"};
  std::cout<< "NumEls = " << sizeof(expenses) / sizeof(expenses[0]) << std::endl;
}

产生10个输出，并更换 COUT 与为循环将使串测试，例如：

produces an output of 10, and replacing the cout with a for loop would allow testing of the strings, for example

for (int i=0; i< (sizeof(expenses)/sizeof(expenses[0])); i++)
{
    std::cout<< "The " << i << "th string is : " << expenses[i] << std::endl;
}

请注意这将产生0号，1号等......

Note this will produce "0th", "1th", etc...

*买者*

反映了这个问题给出的意见，我们没有答案的事实似乎提不完整的的sizeof（指针）不会给你有用的信息 - 或者至少，这没有用。因此，如果你想要，而不是使用方法：

Reflecting the comments given in the question, our answers seem incomplete without mention of the fact that the sizeof(POINTER) won't give you useful information - or at least, not useful for this. As such, if you want instead to use:

myFunction (std::string someArray[])
{
    for( all the strings in someArray )
    {
        std::cout << someArray[i];
    }
}

然后你会发现自己无法做到的。

then you'll find yourself unable to do so.

相反，你可以使用：

myFunction (std::string someArray[], int sizeOfArray)
{
    for(int i=0; i<sizeOfArray; i++)
    {
        std::cout<< someArray[i];
    }
}

但这样的打击究竟你的问题（而不是存储一个单独的INT）

but this goes exactly against your question (not storing a separate int)

*输入的std ::向量*

有一个简单的解决方案是使用的std ::矢量

A simpler solution is to use a std::vector

使用的载体可以为 myVector.size（）函数调用这样也环路上向量的大小自动根据，在更近的情况下，（ C ++ 11）编译器/编译器选项。

The use of a vector allows function calls such as myVector.size() and also loops based automatically on the size of the vector, in the case of more recent (C++11) compilers/compiler options.

矢量可以愉快地传入和传出的功能，如果你想改变他们，向量引用也是一个简单的方法来做到这一点 - 指的是你的答案：

Vectors can be happily passed into and out of functions, and if you want to change them, references to vectors are also a simple way to do so - referring to your answer:

inputFunction (std::vector<string> &expenses, budget &info)
{
    for (int i=0; i< expenses.size(); i++)
    {
        std::cout<< "Enter your expense for " << expenses[i] << ": ";
        // Operation to store input as needed
    }
}

在一个侧面说明，好像要在字符串链接，牺牲为代价的值的名称？如果是这样，也许考虑使用地图。在这种情况下，你可能要考虑的std ::地图＆LT;的std ::字符串，浮动方式＆gt;

On a side note, it seems like you want to link the string for the name of the expense to the value of the expense? If so, consider perhaps using a map. In this case, you'd probably want to consider std::map<std::string, float>.

*使用一个std ::地图*

在使用地图，你可能想的迭代器。一个例子可能是这样的：

In using a map, you'll probably want an iterator. An example might be like:

void input(const std::vector<std::string> &exp, std::map<std::string, float> &map)
{
  for (int i=0; i<exp.size(); i++)
  {
    float tempFloat;
    std::cout<< "Please enter the amount for " << exp[i] << ": ";
    std::cin >> tempFloat;
    map.emplace(exp[i], tempFloat);
  }
};

和的main（），

std::map<std::string, float> myMap;
  input(myVec, myMap);
  for (std::map<std::string, float>::iterator it=myMap.begin(); it!=myMap.end(); it++)
  {
    std::cout << "myMap values -> " << it->first << " = " << it->second << std::endl;
  }

这将输出每对你有使用起 myMap.begin（）的迭代器并在最后进入到地图的结局。

This will output each pair you have, using an iterator starting at myMap.begin() and ending at the last entry to your map.

布设（...）构造一对，然后将其添加到地图中。你应该注意不要使用插入，这就需要一套不同的参数，而不太可能是你想要的这里。

emplace(...) constructs a pair, and then adds it to the map. You should take care not to use insert, which requires a different set of parameters, and is not likely to be what you want here.

的输出由 iterator-＆GT引用$ C>第一和每个地图对第二值。在这种情况下，那些是字符串和浮动存储在地图。

The outputs are referenced by iterator->first and iterator->second, the first and second values of each map pair. In this case, those are the string and float that are stored in the map.

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