c++ string常用函数总结

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c++string常用函数

构造函数

string(const char *s); //用c字符串s初始化
string(int n,char c); //用n个字符c初始化
此外，string类还支持默认构造函数和复制构造函数，如string s1；
string s2=”hello”；都是正确的写法。当构造的string太长而无法表达时会抛出length_error异常 ；

string的特性描述:

int capacity()const; //返回当前容量（即string中不必增加内存即可存放的元素个数）
int max_size()const; //返回string对象中可存放的最大字符串的长度
int size()const; //返回当前字符串的大小
int length()const; //返回当前字符串的长度
bool empty()const; //当前字符串是否为空
void resize(int len,char c);//把字符串当前大小置为len，并用字符c填充不足的部分

子串

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string substr (size_t pos = 0, size_t len = npos) const;

第一个参数默认为0，第二参数默认为字符串结尾的下一个字符。

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#include <iostream>
#include <string>

int main ()
{
    std::string str="We think in generalities, but we live in details.";

    std::string str2 = str.substr (3,5);     // "think"

    std::size_t pos = str.find("live");      // position of "live" in str

    std::string str3 = str.substr (pos);     // get from "live" to the end

    std::cout << str2 << ' ' << str3 << '\n';

    return 0;
}

查找类型

(1) find,rfind这种函数匹配的是指定的连续的数列(当查找的是字符串时)，当参数为字符时，查找的是这个字符出现的位置

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string (1)	
size_t find (const string& str, size_t pos = 0) const;
c-string (2)	
size_t find (const char* s, size_t pos = 0) const;
buffer (3)	
size_t find (const char* s, size_t pos, size_t n) const;
character (4)	
size_t find (char c, size_t pos = 0) const;

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#include <iostream>       // std::cout
#include <string>         // std::string

int main(){
    std::string str ("There are two needles in this haystack with needles.");
    std::string str2 ("needle");

  // different member versions of find in the same order as above:
    std::size_t found = str.find(str2);
    if (found!=std::string::npos)
        std::cout << "first 'needle' found at: " << found << '\n';
    //这里可以指定匹配的字符串的长度，下面的例子匹配长度为6，也就是匹配needle
    found=str.find("needles are small",found+1,6);
    if (found!=std::string::npos)
        std::cout << "second 'needle' found at: " << found << '\n';

    found=str.find("haystack");
    if (found!=std::string::npos)
        std::cout << "'haystack' also found at: " << found << '\n';

    found=str.find('.');
    if (found!=std::string::npos)
        std::cout << "Period found at: " << found << '\n';

  // let's replace the first needle:
    str.replace(str.find(str2),str2.length(),"preposition");
    std::cout << str << '\n';

  return 0;
}

(2) find_first_of，find_first_not_of,find_last_of,find_last_not_of
上面的这四个函数匹配的是给定范围的任意字符，例如

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#include <iostream>       // std::cout
#include <string>         // std::string
#include <cstddef>        // std::size_t

int main ()
{
  std::string str ("Please, replace the vowels in this sentence by asterisks.");
  std::size_t found = str.find_first_of("aeiou");
  while (found!=std::string::npos)
  {
    str[found]='*';
    found=str.find_first_of("aeiou",found+1);
  }

  std::cout << str << '\n';

  return 0;
}

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Pl**s*, r*pl*c* th* v*w*ls *n th*s s*nt*nc* by *st*r*sks.

其它成员函数详见
http://www.cplusplus.com/reference/string/string/