C++中的std :: 字符串:: append()

该成员函数在字符串的末尾附加字符。

1. 语法1：追加字符串str的字符。如果生成的大小超过最大字符数，则将引发length_error。

   string& string::append (const string& str)
   
   str :  is the string to be appended.
   Returns :  *this

   // CPP code to demonstrate append(str)
      
   #include 
   #include 
   using namespace std;
      
   // Function to demonstrate append()
   void appendDemo(string str1, string str2)
   {
       // Appends str2 in str1
       str1.append(str2);
       cout << "Using append() : ";
       cout << str1 << endl;
   }
      
   // Driver code
   int main()
   {
       string str1("Hello World! ");
       string str2("GeeksforGeeks");
      
       cout << "Original String : " << str1 << endl;
       appendDemo(str1, str2);
      
       return 0;
   }
   

   输出：

   Original String : Hello World! 
   Using append() : Hello World! GeeksforGeeks
   

2. 语法2：最多附加字符串str的str_num个字符，从索引str_idx开始。如果str_idx> str，则会抛出out_of_range。尺寸()。如果结果大小超过最大字符数，则抛出length_error。

   string& string::append (const string& str, size_type str_idx, size_type str_num)
   
   str : is the string to be appended
   str_num : being number of characters
   str_idx : is index number.
   Returns : *this.
   

   // CPP code to demonstrate 
   // append(const char* chars, size_type chars_len)
     
   #include 
   #include 
   using namespace std;
      
   // Function to demonstrate append()
   void appendDemo(string str1, string str2)
   {
       // Appends 5 characters from 0th index of
       // str2 to str1
       str1.append(str2, 0, 5);
       cout << "Using append() : ";
       cout << str1;
   }
      
   // Driver code
   int main()
   {
       string str1("GeeksforGeeks ");
       string str2("Hello World! ");
      
       cout << "Original String : " << str1 << endl;
       appendDemo(str1, str2);
      
       return 0;
   }
   

   输出：

   Original String : GeeksforGeeks 
   Using append() : GeeksforGeeks Hello
   

3. 语法3：追加C-串CSTR的字符。如果生成的大小超过最大字符数，则抛出length_error。

   string& string::append (const char* cstr)
   
   *cstr : is the pointer to C-string.
   Note : that cstr may not be a null pointer (NULL).
   Return : *this
   

   // CPP code to demonstrate append(const char* cstr)
     
   #include 
   #include 
   using namespace std;
      
   // Function to demonstrate append
   void appendDemo(string str)
   {
       // Appends "GeeksforGeeks"
       // in str
       str.append("GeeksforGeeks");
       cout << "Using append() : ";
       cout << str << endl;
   }
      
   // Driver code
   int main()
   {
       string str("World of ");
      
       cout << "Original String : " << str << endl;
       appendDemo(str);
      
       return 0;
   }
   

   输出：

   Original String : World of 
   Using append() : World of GeeksforGeeks
   

4. 语法4：追加chars_len字符数组字符的字符。如果生成的大小超过最大字符数，则抛出length_error。

   string& string::append (const char* chars, size_type chars_len)
   
   *chars is the pointer to character array to be appended.
   chrs_len : is the number of characters from *chars to be appended.
   Note that chars must have at least chars_len characters. 
   Returns : *this.
   

   // CPP code to demonstrate 
   // (const char* chars, size_type chars_len)
     
   #include 
   #include 
   using namespace std;
      
   // Function to demonstrate append
   void appendDemo(string str)
   {
       // Appends 5 characters from "GeeksforGeeks"
       // to str
       str.append("GeeksforGeeks", 5);
       cout << "Using append() : ";
       cout << str << endl;
   }
      
   // Driver code
   int main()
   {
       string str("World of ");
      
       cout << "Original String : " << str << endl;
       appendDemo(str);
      
       return 0;
   }
   

   输出：

   Original String : World of 
   Using append() : World of Geeks
   

5. 语法5：追加字符c的出现次数。如果生成的大小超过最大字符数，则抛出length_error。

   string& string::append (size_type num, char c)
   
   num : is the number of occurrences
   c : is the character which is to be appended repeatedly. 
   Returns : *this.
   

   // CPP code to illustrate
   // string& string::append (size_type num, char c)
       
   #include 
   #include 
   using namespace std;
       
   // Function to demonstrate append
   void appendDemo(string str)
   {
       // Appends 10 occurrences of '$'
       // to str
       str.append(10, '$');
       cout << "After append() : ";
       cout << str;
      
   }
              
   // Driver code
   int main()
   {
       string str("#########");
      
       cout << "Original String : " << str << endl;
       appendDemo(str);
       
       return 0;
   }
   

   输出：

   Original String : #########
   After append() : #########$$$$$$$$$$
   

6. 语法6：追加范围[beg，end)的所有字符。如果生成的大小超过最大字符数，则抛出length_error。

   string& string::append (InputIterator beg, InputIterator end)
   
   first, last : Input iterators to the initial and final positions 
   in a sequence.
   Returns *this.
   

   // CPP code  to illustrate
   // append (InputIterator beg, InputIterator end)
      
   #include 
   #include 
   using namespace std;
      
   // Function to demonstrate append
   void appendDemo(string str1, string str2)
   {
      
       // Appends all characters from
       // str2.begin()+5, str2.end() to str1
       str1.append(str2.begin() + 5, str2.end());
       cout << "Using append : ";
       cout << str1;
   }
   // Driver code
   int main()
   {
       string str1("Hello World! ");
       string str2("GeeksforGeeks");
      
       cout << "Original String : " << str1 << endl;
       appendDemo(str1, str2);
      
       return 0;
   }
   

   输出：

   Original String : Hello World! 
   Using append : Hello World! forGeeks
   

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