String (string) class common members -- add +, append, insert, delete erase change replace query find traversal to intercept substring string comparison

Header file and namespace ::

# Include <string>

Using namespace STD;

Use the subscript type for traversal:

String: The size_type type describes the type of the string type lower mark. So the method for traversing the string type is:

For (string: size_type I = 0; I <obj. Size (); I ++)

// The I type cannot be determined because the length is unknown. Only the string: size_type type can be used.

{

Cout <OBJ [I] <Endl; // each member of the variable String object.

}

The const char * type pointer returned by obj. c_str () indicates that the maximum space cannot be assigned by other methods, that is, it cannot be
Left
. For protection purposes.

Important:

OBJ [I] indicates the I + 1 character in the OBJ string. Note:
OBJ [I] can be used as the left value.
. // Very important.

Note:

In some cases, the string class is equivalent to a character container. The string type also supports iterator operations.
.

 

 

Common Operation interfaces of the string class:


 

More operations of the string class
::

1. method for creating a String object:

String STR;

String STR ("Hello World ");

String STR = "Hello World ";

String STR (OBJ); string STR = OBJ;

 

2. Return the first address of the string in the string class: (return the first address of the string type, that is, the conversion from the C string, c_str
)

Const char * P;

P = Str. c_str ();

3. judge whether the string class object is null: (judge whether the string is null, empty
)

String STR;

Str. Empty (); // if it is null, true is returned. Otherwise, false is returned;

 

String Length and string storage capability

4. Obtain the number of characters in a string object: (default string length, size (), length, strlen (*. c_str ())
)

String: size_type size; // note that it must be of the size_type type. (The subscript type of string is size_type)

Str. Resize (number); // The default string stores 100 characters. But it is not actually 100, it does not mean that it can only store 100.

Size = Str. Size (); // obtain the default length of the STR string, which may not be so long.

Size = Str. Length (); // obtain the default length of the STR string, which may not be so long.

Example:

String STR;

Str. Resize (100 );

STR [0] = 'a ';

STR [1] = 'B ';

STR [2] = '/0 ';

Cout <Str. Size () <Endl; // The running result is 100.

Cout <Str. Length () <Endl; // The running result is 100.

Cout <strlen (Str. c_str () <Endl; // The running result is 2, and the true length of the string.

 

Add

5. Two Methods for string connection: (string connection, and append + and append
)

Method 1:

String str1 ("hello ");

String str2 ("world ");

Str1 +
= Str2; // It can also be str1 + = "world.

Method 2:

Str1.append
(Str2 );

6. Insert a string into the string: (insert a string, insert
)

String STR ("Hello World ");

Str. insert
(Pos, "billchen ");

Insert the string "billchen" at the position marked as pos In the STR string ".

Note:

Replacing a substring replace is equivalent to deleting a substring in erase, and then inserting a substring in insert.

Delete

7. delete a substring in a string: (delete the substring, erase
)

String STR ("Hello World ");

Str. Erase
(Pos, Len );

Delete a substring whose subscript starts from POs and is Len.

Note:

Clear the string using the clear () method.

Str. Clear ();

Change

8. replace a substring in a string: (replace the substring, replace
)

String str1 ("Hello World ");

Str1.replace
(Pos, Len, argS );

Delete a substring of the str1 string whose subscript starts from POs and its length is Len, and replace it with the string pointed to by args.

Query

9. Locate a substring in a string: (search for the specified substring in the string, find
)

String STR ("Hello World ");

Str. Find
("Wo"); // search for "wo" in Str"

The subscript of the first position.

Str. rfind
("Wo"); // search for the subscript of the last position of "wo" in Str.

String: size_type Ops = Str. Find ("wo ");

If (Ops = string: NPOs)

{

Cout <"not found" <Endl;

}

It is equivalent to the meaning of strchr and strrchr in C.

Str. find_first_of
(ARGs); // search for the first occurrence of any ARGs characters in Str.

Str. find_last_of
(ARGs); // search for the last occurrence of any ARGs character in Str.

Str. find_first_no_of
(ARGs); // in STR, find the first one that does not belong
ARGs characters.

Str. find_last_no_of
(ARGs); // in STR, find the last one that does not belong
ARGs characters.

Note:

The return values of the find method of the string class are size_type.
Type.

When not found, the returned value is string: NPOs;


You can compare the returned value with string: NOPs to determine whether to locate it.

Traversal

Method 1: subscript

11. Traverse every member of a string:

String STR ("Hello World ");

String: size_type I;

For (I = 0; I <= Str. Size (); I ++)

{

Cout <STR [I] <"";

}

Method 1: iterator
 

11. Traverse every member of a string:

String STR ("Hello World ");

String: iterator iter = Str. Begin ();

While (ITER! = Str. End ())

{

Cout <* ITER <"";

ITER ++;

}

Substring Truncation

12. truncate a substring from a string: (truncate a substring, substr
)

String STR ("Hello World ");

Str. substr (Pos, n); // capture a substring starting from POS with a length of N.

Str. substr (POS); // capture the substring starting from POs to the end of the string.

 

String relationship comparison

13. Judge the relationship between strings.

Equal =

Not Supported! =

Greater than, less than, and equal Relational operators maintain the original meaning.

The C ++ string class also provides the compare method to determine the relationship between strings.