C++ 常用类 string类

===6.3.2使用string对象===

string word="I love China"

*链接字符串*

string description=adjective  + " " + word;

_Note_: 不能连接两个字符串字面量，下面的语句是错误的

string test= "I have" + "a dream";

===6.3.3访问字符串中的字符===

*读取字符串*

getline(cin, text);

getline(cin, text, ‘#‘)_;

word[index];

===6.3.4访问子字符串===

* substr(index0, length);

string phrase = "the higher the fewer";

string wold= phrase.substr(4,6 );

===6.3.5比较字符串===

*操作符*

> >= < !=

*compare()*

world.compare("end");

word.compare(2, 4, "end");

===6.3.6搜索字符串:find===

string sentence = "Manners maketh man";

int a= sentence.find("man");

int b= sentence.find("man", index);//从index开始搜索

如果没有找到，返回~~string:npos~~

*搜索字符集*

string separeators= " ,.\"";

sentence.find_first_of(separeators);

sentence.find_last_of(separeators);

sentence.find_last_not_of(separeators);

sentence.find_first_not_of(separeators);

*逆向搜索*

sentence.rfind("man");

===6.3.7修改字符串:insert、replace、erase===

*1.insert*

_`mystring.insert(index, anotherstring)`

sentence.insert(13, world, 8, 5);//从index=8开始之后的5个字符

把几个相同字符串插入到string对象中：sentence.insert(index,times, string);

*2.replace*

将从index开始的num个字符，替换成新的string：sentence.replace(index, num, string);

*3.erase*

删除从index开始的num个字符：sentence.erase(index, num);

===6.3.8注意事项===

1） append函数与char 和char*

append函数的原型如下：

string& append (const string& str);

string& append (const string& str, size_t subpos, size_t sublen);

string& append (const char* s);

string& append (const char* s, size_t n);

string& append (size_t n, char c);

注意，char* 和char用作append的参数时候，例如，想在string尾部增加一个字符，需要用mystring.append(1, ch) 而不是mystring.apend(ch). 同样，想将chars的其中一部分插入string中，需要用mystring.append(s+a, b-a)

注意，如果仅仅想增加一个字符，使用push_back即可

string 详解

1.*string constructor*

default (1) string();

copy (2) string (const string& str);

substring (3) string (const string& str, size_t pos, size_t len = npos);

from c-string (4) string (const char* s);

from buffer (5) string (const char* s, size_t n);

fill (6) string (size_t n, char c);

range (7) template <class InputIterator>

string  (InputIterator first, InputIterator last);

// string constructor
#include <iostream>
#include <string>

int main ()
{
  std::string s0 ("Initial string");
  // constructors used in the same order as described above:
  std::string s1;
  std::string s2 (s0);
  std::string s3 (s0, 8, 3);
  std::string s4 ("A character sequence", 6);
  std::string s5 ("Another character sequence");
  std::string s6 (10, 'x');
  std::string s7a (10, 42);      // 42 is the ASCII code for '*'
  std::string s7b (s0.begin(), s0.begin()+7);
  std::cout << "s1: " << s1 << "\ns2: " << s2 << "\ns3: " << s3;
  std::cout << "\ns4: " << s4 << "\ns5: " << s5 << "\ns6: " << s6;
  std::cout << "\ns7a: " << s7a << "\ns7b: " << s7b << '\n';
  return 0;
}
**output**:
s1:
s2: Initial string
s3: str
s4: A char
s5: Another character sequence
s6: xxxxxxxxxx
s7a: **********
s7b: Initial

2.迭代器：

begin();

end();

3.capacity:

size();

length();

clear();

empty();

4.Element Access:

operator[]

at()

back();

front();

5.Modifier

operator+=

append()

push_back()

assign()

insert()

erase()

replcace();

swap();

pop_back();

6.String Operations:

copy();

find();

find_first_of();

find_last_of();

find_first_not_of();

find_last_not_of();

substr();

compare();

7.Member constants:

npos

8.Non-member function overloads:

getline();

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