Is there a way to use a tolower() like function on a vector<string> variable in C++?

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英文:

Is there a way to use a tolower() like function on a vector<string> variable in C++?

问题

I'm trying to load and sort a file alphabetically. To make this easier, I have to convert the characters to lowercase.

Now, do I have to do this character-by-character as I read it into a string array (because tolower() only accepts characters), or can I somehow use it with a vector<string> container?

Here's the code:

#include <iostream>
#include <fstream>
#include <cstring>
#include <vector>

using namespace std;

int main() {

   ifstream file("phoneNumbers.txt");
   vector<string> wordStream;
   int i = 0;

    if (file.fail()) {
        cout << "Couldn't open file!";
        return 1;
    }

    while(file >> wordStream[i]) {
        wordStream[i] = tolower(wordStream[i]);
        ++i;
    }
}

Newbie question, I know.

I already tried the std::transform() function that someone recommended on StackOverflow, but still it didn't work.

英文:

I'm trying to load and sort a file alphabetically. To make this easier, I have to convert the characters to lowercase.

Now, do I have to do this character-by-character as I read it into a string array (because tolower() only accepts characters), or can I somehow use it with a vector&lt;string&gt; container?

Here's the code:

#include &lt;iostream&gt;
#include &lt;fstream&gt;
#include &lt;cstring&gt;
#include &lt;vector&gt;

using namespace std;

int main() {

   ifstream file(&quot;phoneNumbers.txt&quot;);
   vector&lt;string&gt; wordStream;
   int i = 0;

    if (file.fail()) {
        cout &lt;&lt; &quot;Couldn&#39;t open file!&quot;;
        return 1;
    }

    while(file&gt;&gt;wordStream[i]) {
        wordStream[i] = tolower(wordStream[i]);
        ++i;
    }
}

Newbie question, I know.

I already tried the std::transform() function that someone recommended on StackOverflow, but still it didn't work.

答案1

得分: 3

你的代码有两个问题,`tolower` 在字符串上不起作用,并且你的向量大小为零,所以对于任何`i`的值,`wordStream[i]`都会报错。以下是修复了这些错误的代码:

    string temp;
    while (file >> temp) { // 读入一个临时字符串
        // 将字符串转换为小写
        std::transform(temp.begin(), temp.end(), temp.begin(), tolower);
        // 将临时字符串添加到向量中
        wordStream.push_back(temp);
    }
英文:

Your code has two problems, tolower doesn't work on strings, and your vector has a size of zero so wordStream[i] is an error for any value of i. Here's the code fixed of those errors

string temp;
while (file &gt;&gt; temp) { // read to a temporary string
    // convert string to lower case
    std::transform(temp.begin(), temp.end(), temp.begin(), tolower);
    // add temporary string to vector
    wordStream.push_back(temp);
}

huangapple
  • 本文由 发表于 2023年5月18日 04:07:59
  • 转载请务必保留本文链接:https://go.coder-hub.com/76275852.html
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