C++之string

头文件 #include<string>

支持长度可变的字符串。

1、string对象的定义和初始化

string s1; //默认构造函数，s1为空串string s2(s1); //将s2初始化为s1的一个副本string s3("value"); //将s3初始化为一个字符串字面值副本string s4(n, 'c'); //将s4初始化为字符'c'的n个副本

2、string对象的读写

int main(){    string s;    cin >> s;    cout << s << endl;    return 0;}

⚠️：string类型的输入操作符：

读取并忽略开头所有的空白字符（如空格、换行符、制表符）；

读取字符直至再次遇到空白字符，读取终止。

用get line读取整行文本：

int main() {    string s;    while( get line(cin, s) ) {        cout << s << endl;    }}

换行符将不会存储在string对象中

3、string iterators

begin

Return iterator to beginning (public member function )

end

Return iterator to end (public member function )

rbegin

Return reverse iterator to reverse beginning (public member function )

rend

Return reverse iterator to reverse end (public member function )

cbegin 

Return const_iterator to beginning (public member function )

cend 

Return const_iterator to end (public member function )

crbegin 

Return const_reverse_iterator to reverse beginning (public member function )

crend 

Return const_reverse_iterator to reverse end (public member function )

4、string Capacity:

size

Return length of string (public member function )

length

Return length of string (public member function )

max_size

Return maximum size of string (public member function )

resize

Resize string (public member function )

capacity

Return size of allocated storage (public member function )

reserve

Request a change in capacity (public member function )

clear

Clear string (public member function )

empty

Test if string is empty (public member function )

shrink_to_fit 

Shrink to fit (public member function )

5、Element access:

operator[]

Get character of string (public member function )

at

Get character in string (public member function )

back 

Access last character (public member function )

front 

Access first character (public member function )

6、Modifiers:

operator+=

Append to string (public member function )

append

Append to string (public member function )

push_back

Append character to string (public member function )

assign

Assign content to string (public member function )

insert

Insert into string (public member function )

erase

Erase characters from string (public member function )

replace

Replace portion of string (public member function )

swap

Swap string values (public member function )

pop_back 

Delete last character (public member function )

7、String operations:

c_str

Get C string equivalent (public member function )

data

Get string data (public member function )

get_allocator

Get allocator (public member function )

copy

Copy sequence of characters from string (public member function )

find

Find content in string (public member function )

rfind

Find last occurrence of content in string (public member function )

find_first_of

Find character in string (public member function )

find_last_of

Find character in string from the end (public member function )

find_first_not_of

Find absence of character in string (public member function )

find_last_not_of

Find non-matching character in string from the end (public member function )

substr

Generate substring (public member function )

compare

Compare strings (public member function )

8、Non-member function overloads

operator+

Concatenate strings (function )

relational operators

Relational operators for string (function )

swap

Exchanges the values of two strings (function )

operator>>

Extract string from stream (function )

operator<<

Insert string into stream (function )

getline

Get line from stream into string (function )

9、Member constants

npos

Maximum value for size_t (public static member constant )

10、对单个字符的处理

isalnum(c); //如果c为字母或者数字，就返回trueisalpha(c); //如果c为字母，则返回trueisdigit(c); //数字islower(c); //小写字母isupper(c); //大写字母isspace(c); //空白字符tolower(c); //如果是大写字母，返回其小写形式，否则直接返回ctoupper(c); //如果是小写字母，返回其大写字母形式，否则直接返回cisxdigit(c); //十六进制