c++string类库的一些用法《一》

深藏阁楼爱情的钟 2022-06-17 22:29 202阅读 0赞

1.string类对象的插入insert方法，

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   <td style="border:1px solid rgb(192,192,208); vertical-align:top; background:rgb(239,239,255)"> <pre style="margin-top:0px; margin-bottom:0px"><code>#include &lt;iostream&gt;
#include &lt;string&gt;

int main ()
{
  std::string str="to be question";
  std::string str2="the ";
  std::string str3="or not to be";
  std::string::iterator it;

<cite style="font-style:normal; color:rgb(0,112,0)">// used in the same order as described above:</cite>
  str.insert(6,str2);                 <cite style="font-style:normal; color:rgb(0,112,0)">// to be (the )question</cite>
  str.insert(6,str3,3,4);             <cite style="font-style:normal; color:rgb(0,112,0)">// to be (not )the question</cite>
  str.insert(10,"that is cool",8);    <cite style="font-style:normal; color:rgb(0,112,0)">// to be not (that is )the question</cite>
  str.insert(10,"to be ");            <cite style="font-style:normal; color:rgb(0,112,0)">// to be not (to be )that is the question</cite>
  str.insert(15,1,':');               <cite style="font-style:normal; color:rgb(0,112,0)">// to be not to be(:) that is the question</cite>
  it = str.insert(str.begin()+5,','); <cite style="font-style:normal; color:rgb(0,112,0)">// to be(,) not to be: that is the question</cite>
  str.insert (str.end(),3,'.');       <cite style="font-style:normal; color:rgb(0,112,0)">// to be, not to be: that is the question(...)</cite>
  str.insert (it+2,str3.begin(),str3.begin()+3); <cite style="font-style:normal; color:rgb(0,112,0)">// (or )</cite>

std::cout &lt;&lt; str &lt;&lt; '\n';
  return 0;
}</code></pre> </td> 
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2. .string类对象的替换 `replace` 方法，

#include <iostream>
    #include <string>
    
    int main ()
    {
      std::string base="this is a test string.";
      std::string str2="n example";
      std::string str3="sample phrase";
      std::string str4="useful.";
    
      // replace signatures used in the same order as described above:
    
      // Using positions: 0123456789*123456789*12345
      std::string str=base;           // "this is a test string."
      str.replace(9,5,str2);          // "this is an example string." (1)
      str.replace(19,6,str3,7,6);     // "this is an example phrase." (2)
      str.replace(8,10,"just a");     // "this is just a phrase." (3)
      str.replace(8,6,"a shorty",7);  // "this is a short phrase." (4)
      str.replace(22,1,3,'!');        // "this is a short phrase!!!" (5)
    
      // Using iterators: 0123456789*123456789*
      str.replace(str.begin(),str.end()-3,str3);                    // "sample phrase!!!" (1)
      str.replace(str.begin(),str.begin()+6,"replace");             // "replace phrase!!!" (3)
      str.replace(str.begin()+8,str.begin()+14,"is coolness",7);    // "replace is cool!!!" (4)
      str.replace(str.begin()+12,str.end()-4,4,'o');                // "replace is cooool!!!" (5)
      str.replace(str.begin()+11,str.end(),str4.begin(),str4.end());// "replace is useful." (6)
      std::cout << str << '\n';
      return 0;
    }

3. string类对象的查找find 方法

// string::find
    #include <iostream> // std::cout
    #include <string> // std::string
    
    int main ()
    {
      std::string str ("There are two needles in this haystack with needles.");
      std::string str2 ("needle");
    
      // different member versions of find in the same order as above:
      std::size_t found = str.find(str2);
      if (found!=std::string::npos)
        std::cout << "first 'needle' found at: " << found << '\n';
    
      found=str.find("needles are small",found+1,6);
      if (found!=std::string::npos)
        std::cout << "second 'needle' found at: " << found << '\n';
    
      found=str.find("haystack");
      if (found!=std::string::npos)
        std::cout << "'haystack' also found at: " << found << '\n';
    
      found=str.find('.');
      if (found!=std::string::npos)
        std::cout << "Period found at: " << found << '\n';
    
      // let's replace the first needle:
      str.replace(str.find(str2),str2.length(),"preposition");
      std::cout << str << '\n';
    
      return 0;
    }

输出结果：

first 'needle' found at: 14
    second 'needle' found at: 44
    'haystack' also found at: 30
    Period found at: 51
    There are two prepositions in this haystack with needles.