字符串下标超出范围.字符串大小未知，并且循环字符串直到为空 [英] String subscript out of range. String size is unknown and looping string until null

问题描述

#include<iostream>
#include<cmath>
#include<iomanip>
#include<string>

using namespace std;

int main()
{
 string word;
 int j = 0;

 cin >> word;

 while(word[j]){
 cout << "idk";
 j++;
 }
 cout << "nope";



 system("pause");
 return 0;
}

这只是一个小试验程序，用于测试此循环.我正在研究的程序是有关元音和按照用户确定的顺序打印元音的.直到用户键入该字符串才定义.谢谢您的帮助.

This is just a little trial program to test this loop out. The program I am working on is about vowels and printing vowels out from a sequence determined by the user. The string isn't defined until the user types in. Thank you for your guys help in advance.

推荐答案

std::string的大小不是 未知-您可以使用std::string::size()成员函数来获取它.还要注意，与C字符串不同，std::string类不必以空值结尾，因此您不能依赖空值字符来终止循环.

The size of an std::string is not unknown - you can get it using the std::string::size() member function. Also note that unlike C-strings, the std::string class does not have to be null-terminated, so you can't rely on a null-character to terminate a loop.

实际上，与std::string一起使用会更好，因为您始终知道大小.与所有C ++容器一样，std::string也带有内置的迭代器，可让您安全地循环遍历字符串中的每个字符. std::string::begin()成员函数为您提供一个指向字符串开头的迭代器，而std::string::end()函数为您提供一个指向最后一个字符之后的迭代器.

In fact, it's much nicer to work with std::string because you always know the size. Like all C++ containers, std::string also comes with built-in iterators, which allow you to safely loop over each character in the string. The std::string::begin() member function gives you an iterator pointing to the beginning of the string, and the std::string::end() function gives you an iterator pointing to one past the last character.

我建议您熟悉C ++迭代器.使用迭代器处理字符串的典型循环如下所示:

I'd recommend becoming comfortable with C++ iterators. A typical loop using iterators to process the string might look like:

for (std::string::iterator it = word.begin(); it != word.end(); ++it)
{
   // Do something with the current character by dereferencing the iterator
   // 
   *it = std::toupper(*it); // change each character to uppercase, for example
}

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