C++ string
C++ provides the following two types of string representations:
C-style string
The string class type introduced in C++
C-style string
C-style string originated from the C language and continues to be supported in C++. A string is actually a one-dimensional character array terminated with the null character '\0'. Therefore, a null-terminated string contains the characters that make up the string.
The following declaration and initialization creates a "Hello" string. The size of the character array is one more than the number of characters of the word "Hello" because a null character is stored at the end of the array.
char greeting[6] = {'H', 'e', 'l', 'l', 'o', 'char greeting[] = "Hello";
'};According to the array initialization rules, you can write the above statement as the following statement:
#include <iostream>
using namespace std;
int main ()
{
char greeting[6] = {'H', 'e', 'l', 'l', 'o', 'Greeting message: Hello
'};
cout << "Greeting message: ";
cout << greeting << endl;
return 0;
}The following is the memory representation of the string defined in C/C++:
Actually, you don't need to put the null character at the end of the string constant. The C++ compiler will automatically put '\0' at the end of the string when initializing the array. Let us try to output the above string:
#include <iostream>
#include <cstring>
using namespace std;
int main ()
{
char str1[10] = "Hello";
char str2[10] = "World";
char str3[10];
int len ;
// 复制 str1 到 str3
strcpy( str3, str1);
cout << "strcpy( str3, str1) : " << str3 << endl;
// 连接 str1 和 str2
strcat( str1, str2);
cout << "strcat( str1, str2): " << str1 << endl;
// 连接后，str1 的总长度
len = strlen(str1);
cout << "strlen(str1) : " << len << endl;
return 0;
}When the above code is compiled and executed, it will produce the following results:
strcpy( str3, str1) : Hello strcat( str1, str2): HelloWorld strlen(str1) : 10
There are a large number of functions in C++ for operating with null Terminated strings: supports a wide range of functions that manipulate null-terminated strings:
| serial number | function&purpose |
|---|---|
| 1 | strcpy(s1, s2); Copy string s2 to string s1. |
| 2 | strcat(s1, s2); Concatenate string s2 to the end of string s1. |
| 3 | strlen(s1); Returns the length of string s1. |
| 4 | strcmp(s1, s2); If s1 and s2 are the same, return 0; if s1< If s2, it returns less than 0; if s1>s2, it returns greater than 0. |
| 5 | strchr(s1, ch); Returns a pointer pointing to the first character ch in string s1 The location where it appears. |
| 6 | strstr(s1, s2); Returns a pointer pointing to the first string s2 in string s1 The position where it appears. |
The following example uses some of the above functions:
#include <iostream>
#include <string>
using namespace std;
int main ()
{
string str1 = "Hello";
string str2 = "World";
string str3;
int len ;
// 复制 str1 到 str3
str3 = str1;
cout << "str3 : " << str3 << endl;
// 连接 str1 和 str2
str3 = str1 + str2;
cout << "str1 + str2 : " << str3 << endl;
// 连接后，str3 的总长度
len = str3.size();
cout << "str3.size() : " << len << endl;
return 0;
}When the above code is compiled and executed, it will produce the following results:
str3 : Hello str1 + str2 : HelloWorld str3.size() : 10
String class in C++
The C++ standard library provides the string class type, which supports all the above operations, and also adds other more functions. We will study this class in the C++ standard library. Now let's take a look at the following example:
You may not understand this example thoroughly now because we have not discussed classes and objects so far. . So now you can just take a quick look at this example and come back to it later when you understand the object-oriented concepts.
rrreeeWhen the above code is compiled and executed, it produces the following results:
rrreee
