C++:追加到 vector 字符串

Question

我正在编写一个“ pig 拉丁语”程序；读取用户的输入(名字和姓氏)使输入小写并根据名称中的内容更改名称。如果第一个字母(名字和姓氏)是元音，我们应该在它的末尾添加“way”。

如果第一个字母是辅音，我们就把第一个字母移到字符串的末尾，然后在末尾添加“ay”。

在尝试向字符串末尾添加文本时，我的代码一直出错。它说它不能将字符串转换为字符，我不确定那是什么意思。它还说我不能将输出操作数 << 用于字符串，即使我以前使用过它也是如此。

错误出现在“strcpy”和我输出名称的最终代码中。

37: error: cannot convert 'std::vector<std::basic_string<char, std::char_traits<char>, std::allocator<char> >, std::allocator<std::basic_string<char, std::char_traits<char>, std::allocator<char> > > >' to 'char*' for argument '1' to 'char* strcpy(char*, const char*)'

47: error: cannot convert 'std::vector<std::basic_string<char, std::char_traits<char>, std::allocator<char> >, std::allocator<std::basic_string<char, std::char_traits<char>, std::allocator<char> > > >' to 'char*' for argument '1' to 'char* strcpy(char*, const char*)'

54: error: no match for 'operator<<' in 'std::cout << first'

我只需要一些帮助来修复错误并查看我哪里出错了。包含完整代码。

#include <iostream>
#include <vector>
#include <cstring>
#include <string>
using namespace std;
int main()
{
    int q, s;
    char shea[] = "way";
    char gavin_stop_looking_at_ponies[] = "ay";
    vector <string> first;
    vector <string> last;
    cout << "Please enter your first name." << endl;
    for (int i = 0; i < first.size(); i++)
    {
        getline (cin, first[i]);
        string nfirst = first[i];
        while (nfirst[q])
        {
            nfirst[q] = tolower(nfirst[q]);
        }
        first[i] = nfirst;
    }
    cout << "Please enter your last name." << endl;
    for (int j = 0; j < last.size(); j++)
    {
        getline (cin, last[j]);
        string nlast = last[j];
        while (nlast[s])
        {
            nlast[s] = tolower(nlast[s]);
        }
        last[j] = nlast;
        }
    if ( (first[0] == "a") ||( first [0] == "e") || (first [0] == "i") || (first [0] == "o")     || (first [0] == "u"))
    {
        strcpy (first, "way");
    }
    else
    {
        first[first.size()] = first[0] + "ay";
    }
    
    if ( (last[0] == "a") ||( last [0] == "e") || (last [0] == "i") || (last [0] == "o") || (last [0] == "u"))
    {
        strcpy (last, "way");
    }
    else
    {
        last[last.size()] = last[0] + "ay";
    }
    cout << first << last << endl;
    return 0;
}

Answer 1

我已经在您的代码中注释了一些问题和解决方案的建议。如果您有任何不明白的地方，请发表评论，我会尽力澄清。

#include <iostream>

// You don't need 'vector' for this.
<del>#include <vector></del>

// You won’t often need the C string header in C++.
<del>#include <cstring></del>

#include <string>
using namespace std;
int main()
{
    // These variables are unused.
<del>    int q, s;
    char shea[] = "way";
    char gavin_stop_looking_at_ponies[] = "ay";</del>

    // 'first' and 'last' are both names, not collections
    // of names.
    <strong>string first;</strong>
    <strong>string last;</strong>
    <del>vector <string> first;</del>
    <del>vector <string> last;</del>

    // 'endl' is unnecessary here; it outputs a newline and
    // flushes the stream, but standard output is usually
    // line-buffered, meaning that newline flushes the
    // stream regardless.
    <strong>cout << "Please enter your first name.\n"</strong>
    <del>cout << "Please enter your first name." << endl;</del>

    // If you just want to get one name, 'getline' is perfect.
    <strong>getline(cin, first);</strong>

    // This loop would run 0 times because 'first' is an
    // empty vector.
<del>    for (int i = 0; i < first.size(); i++)
    {
        getline (cin, first[i]);
        string nfirst = first[i];
        while (nfirst[q])
        {
            nfirst[q] = tolower(nfirst[q]);
        }
        first[i] = nfirst;
    }</del>

    // To make a string lowercase, use 'tolower' on each character.
    // Here's one way to do it:
    <strong>for (string::size_type i = 0; i < first.size(); ++i)
        first[i] = tolower(first[i]);</strong>

    // Here's another, with C++11 enabled:
    <strong>for (auto& c : first)
        c = tolower(c);</strong>

    <strong>cout << "Please enter your last name.\n";</strong>
    <del>cout << "Please enter your last name." << endl;</del>

    // Same thing.
    <strong>getline(cin, last);</strong>
<del>    for (int j = 0; j < last.size(); j++)
    {
        getline (cin, last[j]);
        string nlast = last[j];
        while (nlast[s])
        {
            nlast[s] = tolower(nlast[s]);
        }
        last[j] = nlast;
    }</del>

    // Now 'first' is a string, and 'first[0]' is a 'char'.
    // "a" is a string literal; 'a' is a character literal.
    // You can compare each character individually:
<strong>    if (first[0] == 'a' || first[0] == 'e' || first[0] == 'i' || first[0] == 'o' || first[0] == 'u')</strong>

    // Or you can say "if the character was found in this
    // set of vowels".
<strong>    if (string("aeiou").find(first[0]) != string::npos)</strong>

<del>    if ( (first[0] == "a") ||( first [0] == "e") || (first [0] == "i") || (first [0] == "o")     || (first [0] == "u"))</del>
    {
        // This would try to copy "way" into 'first':
        // formerly a vector of string objects, now just a
        // string object. 'strcpy' wants a character buffer,
        // and will <em>overwrite</em> characters in that buffer—
        // probably not what you want:
        //
        // "aaron" => "wayon"
        // 
        <del>strcpy (first, "way");</del>

        // Instead, just append "way":
        <strong>first += "way";</strong>
    }
    else
    {
        // This says "take the first first character of the
        // string, add the value of that character to a
        // pointer to a buffer containing "ay", then try to
        // copy the resulting pointer past the end of the
        // string. Again, not quite what you intended!
        <del>first[first.size()] = first[0] + "ay";</del>

        // Think of it instead like this: take everything
        // after the first character, add a string consisting
        // of the first character back onto the end, then add
        // "ay" after that.
        <strong>first = first.substr(1) + string(1, first[0]) + "ay";</strong>
    }

    // Duplicated code! You could move the above logic into
    // a function to avoid this duplication. Then you only
    // have to work on it in one place. :)
<del>    if ( (last[0] == "a") ||( last [0] == "e") || (last [0] == "i") || (last [0] == "o") || (last [0] == "u"))
    {
        strcpy (last, "way");
    }
    else
    {
        last[last.size()] = last[0] + "ay";
    }</del>

    // I need a space between my first and last names!
    <strong>cout << first << ' ' << last << '\n';</strong>
    <del>cout << first << last << endl;</del>
    return 0;
}