STL--string用法(1)

• 1. 先打开文件，检测文件是否打开，如果失败，则退出。
  2. 声明一个足够大得二维字符数组或者一个字符指针数组
  3. 读入一行到字符空间
  4. 然后分析一行的结构，找到空格，存入字符数组中。
  5. 关闭文件
  6. 写一个排序函数，或者使用写一个比较函数，使用qsort排序
  7. 遍历数组，比较是否有相同的，如果有，则要删除，copy...
  8. 输出信息
  1. c_str 直接返回一个以/0结尾的字符串。
  2. data 直接以数组方式返回string的内容，其大小为size()的返回值，结尾并没有/0字符。
  3. copy 把string的内容拷贝到buf空间中。
  1. 定义分隔符。给定分隔符，把string分为几个字段。
  2. 提供替换功能。例如，用winter, 替换字符串中的wende
  3. 大小写处理。例如，忽略大小写比较，转换等
  4. 整形转换。例如把"123"字符串转换为123数字。

STL----string

今天看stl中的string得：

一 问题：

举例来说，如果文本格式是：用户名 电话号码，文件名name.txt

Tom 23245332
Jenny 22231231
Heny 22183942
Tom 23245332
...

现在我们需要对用户名排序，且只输出不同的姓名。

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如果使用C/C++ 就麻烦了，他需要做以下工作：

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我们可以使用 fstream来代替麻烦的fopen fread fclose, 用vector 来代替数组。最重要的是用 string来代替char * 数组，使用sort排序算法来排序，用unique 函数来去重。听起来好像很不错 。看看下面代码(例程1）：

#include <string>
#include <iostream>
#include <algorithm>
#include <vector>
#include <fstream>
using namespace std;
int main(){
ifstream in("name.txt");
string strtmp;
vector<string> vect;
while(getline(in, strtmp, '/n'))
vect.push_back(strtmp.substr(0, strtmp.find(' ')));
sort(vect.begin(), vect.end());
vector<string>::iterator it=unique(vect.begin(), vect.end());
copy(vect.begin(), it, ostream_iterator<string>(cout, "/n"));
return 0;
}

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二

string 函数列表

http://www.cplusplus.com/reference/string/string/(用法)

函数名	描述
begin	得到指向字符串开头的Iterator
end	得到指向字符串结尾的Iterator
rbegin	得到指向反向字符串开头的Iterator
rend	得到指向反向字符串结尾的Iterator
size	得到字符串的大小
length	和size函数功能相同
max_size	字符串可能的最大大小
capacity	在不重新分配内存的情况下，字符串可能的大小
empty	判断是否为空
operator[]	取第几个元素，相当于数组
c_str	取得C风格的const char* 字符串
data	取得字符串内容地址
operator=	赋值操作符
reserve	预留空间
swap	交换函数
insert	插入字符
append	追加字符
push_back	追加字符
operator+=	+= 操作符
erase	删除字符串
clear	清空字符容器中所有内容
resize	重新分配空间
assign	和赋值操作符一样
replace	替代
copy	字符串到空间
find	查找
rfind	反向查找
find_first_of	查找包含子串中的任何字符，返回第一个位置
find_first_not_of	查找不包含子串中的任何字符，返回第一个位置
find_last_of	查找包含子串中的任何字符，返回最后一个位置
find_last_not_of	查找不包含子串中的任何字符，返回最后一个位置
substr	得到字串
compare	比较字符串
operator+	字符串链接
operator==	判断是否相等
operator!=	判断是否不等于
operator<	判断是否小于
operator>>	从输入流中读入字符串
operator<<	字符串写入输出流
getline	从输入流中读入一行

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三 string提供了三个函数满足其要求：

const charT* c_str() const
const charT* data() const
size_type copy(charT* buf, size_type n, size_type pos = 0) const

其中：

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四 basic_string 是基于字符序列容器(Sequence)的模板类, 包含了说有序列容器的常用操作，同时也包含了字符串的标准操作，如"查找"和"合并" 。

typedef basic_string <char> string;

typedef basic_string<wchar_t> wstring;

五 Extended STL string

ext_string，提供一些常用的功能，例如：

附录：ext_string：

/**

* @mainpage Extended STL string

* @author Keenan Tims - [email protected]

* @version 0.2

* @date 2005-04-17

* @section desc Description

* ext_string aims to provide a portable, bug-free implementation of many useful extensions to the

* standard STL string class. These extensions are commonly available among higher-level languages

* such as Perl and Python, but C++ programmers are generally left on their own when it comes to

* basic string processing. By extending the STL's string, we can provide a drop-in replacement for STL

* strings with the greater functionality of higher-level languages.

*

* The primary goal of this library is to make the STL string class more usable to programmers that

* are doing simple string manipulation on a small scale. Due to the usability goals of this class,

* many actions will be inefficiently implemented for the sake of ease of use. Some of this is

* mitigated somewhat by doing modification in-place, however many unnecessary copies of data are

* created by some methods, and the vector-returning methods are inefficient in that they copy the

* substrings into the vector, then return a copy of the vector. This would be much more efficient

* as an iterator model.

*

*

* @section feat Features

*

* @li Fully based on the STL, ext_string provides a superset of std::string methods

* @li String splitting (tokenizing), on a character, a string, or whitespace

* @li Replacement of substrings or characters with another string or character

* @li String case operations (check, adjust)

* @li Integer conversion

* @li Fully open-source under a BSD-like license for use in any product

*

* @if web

* @section download Downloads

*

* Downloads are provided in tar.gz and zip formats containing this documentation, the header file,

* and the library's changelog. The latest version of ext_string is 0.2, released on April 17,

* 2005.

*

* @li<a href="files/ext_string-0.2.tar.gz">ext_string-0.2.tar.gz</a>

* @li<a href="files/ext_string-0.2.zip">ext_string-0.2.zip</a>

* @li <small><a href="files/ext_string-0.1.tar.gz">ext_string-0.1.tar.gz</a></small>

* @li <small><a href="files/ext_string-0.1.zip">ext_string-0.1.zip</a></small>

*

* @section changelog Changelog

*

* The changelog is viewable online <a href="files/CHANGELOG">here</a>

*

* @endif

*

* @section notes Notes/Limitations

* @li Copying all the substrings into a vector for the substring methods is pretty inefficient,

* both for space and time. It would be more prudent to model an iterator to split the string based

* on the specified parameters, but this is more difficult to implement and more cumbersome to use.

* Performance is not the main goal of this library, usability is, thus the tradeoff is deemed to be

* acceptable.

* @li References are not used too aptly in this class. Some performance tuning could be done to

* minimize unnecessary data copying.

* @li The basic methods of std::string aren't overridden by this class, thus assigning the return

* value of eg. string::insert() to an ext_string instance will make an unnecessary string object

* which is then copy-constructed to an ext_string (I believe, internal workings of inheritance and

* polymorphism in C++ are somewhat beyond my experience). These methods should be wrapped by

* ext_string to return the proper type.

*

*

* @section related Related Documentation

*

* @li SGI's STL string reference: http://www.sgi.com/tech/stl/basic_string.html

*

*

* @section license License

*

* Copyright (c) 2005, Keenan Tims

* All rights reserved.

*

* Redistribution and use in source and binary forms, with or without modification, are permitted

* provided that the following conditions are met:

* @li Redistributions of source code must retain the above copyright notice, this list of

* conditions and the following disclaimer.

* @li Redistributions in binary form must reproduce the above copyright notice, this list of

* conditions and the following disclaimer in the documentation and/or other materials provided with

* the distribution.

* @li Neither the name of the Extended STL String project nor the names of its contributors may be used to endorse

* or promote products derived from this software without specific prior written permission.

*

* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR

* IMPLIED WARRANTIES, INCLUDING BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTIBILITY AND

* FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR

* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL

* DAMAGES (INCLUDING BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,

* DATA OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER

* IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT

* OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

*

*

*/

#ifndef _EXT_STRING_H

#define _EXT_STRING_H

#include <string>

#include <vector>

namespace std

{

/**

* An extension of STL's string providing additional functionality that is often availiable in

* higher-level languages such as Python.

*/

class ext_string : public string

{

public:

/**

* Default constructor

*

* Constructs an empty ext_string ("")

*/

ext_string() : string() { }

/**

* Duplicate the STL string copy constructor

*

* @param[in] s The string to copy

* @param[in] pos The starting position in the string to copy from

* @param[in] n The number of characters to copy

*/

ext_string(const string &s, size_type pos = 0, size_type n = npos) : string(s, pos, npos) { }

/**

* Construct an ext_string from a null-terminated character array

*

* @param[in] s The character array to copy into the new string

*/

ext_string(const value_type *s) : string(s) { }

/**

* Construct an ext_string from a character array and a length

*

* @param[in] s The character array to copy into the new string

* @param[in] n The number of characters to copy

*/

ext_string(const value_type *s, size_type n) : string(s, n) { }

/**

* Create an ext_string with @p n copies of @p c

*

* @param[in] n The number of copies

* @param[in] c The character to copy @p n times

*/

ext_string(size_type n, value_type c) : string(n, c) { }

/**

* Create a string from a range

*

* @param[in] first The first element to copy in

* @param[in] last The last element to copy in

*/

template <class InputIterator>

ext_string(InputIterator first, InputIterator last) : string(first, last) { }

/**

* The destructor

*/

~ext_string() { }

/**

* Split a string by whitespace

*

* @return A vector of strings, each of which is a substring of the string

*/

vector<ext_string> split(size_type limit = npos) const

{

vector<ext_string> v;

const_iterator

i = begin(),

last = i;

for (; i != end(); i++)

{

if (*i == ' ' || *i == '/n' || *i == '/t' || *i == '/r')

{

if (i + 1 != end() && (i[1] == ' ' || i[1] == '/n' || i[1] == '/t' || i[1] == '/r'))

continue;

v.push_back(ext_string(last, i));

last = i + 1;

if (v.size() >= limit - 1)

{

v.push_back(ext_string(last, end()));

return v;

}

}

}

if (last != i)

v.push_back(ext_string(last, i));

return v;

}

/**

* Split a string by a character

*

* Returns a vector of ext_strings, each of which is a substring of the string formed by splitting

* it on boundaries formed by the character @p separator. If @p limit is set, the returned vector

* will contain a maximum of @p limit elements with the last element containing the rest of

* the string.

*

* If @p separator is not found in the string, a single element will be returned in the vector

* containing the entire string.

*

* The separators are removed from the output

*

* @param[in] separator The character separator to split the string on

* @param[in] limit The maximum number of output elements

* @return A vector of strings, each of which is a substring of the string

*

* @section split_ex Example

* @code

* std::ext_string s("This|is|a|test.");

* std::vector<std::ext_string> v = s.split('|');

* std::copy(v.begin(), v.end(), std::ostream_iterator<std::ext_string>(std::cout, "/n"));

*

* This

* is

* a

* test.

* @endcode

*/

vector<ext_string> split(value_type separator, size_type limit = npos) const

{

vector<ext_string> v;

const_iterator

i = begin(),

last = i;

for (; i != end(); i++)

{

if (*i == separator)

{

v.push_back(ext_string(last, i));

last = i + 1;

if (v.size() >= limit - 1)

{

v.push_back(ext_string(last, end()));

return v;

}

}

}

if (last != i)

v.push_back(ext_string(last, i));

return v;

}

/**

* Split a string by another string

*

* Returns a vector of ext_strings, each of which is a substring of the string formed by

* splitting it on boundaries formed by the string @p separator. If @p limit is set, the

* returned vector will contain a maximum of @p limit elements with the last element

* containing the rest of the string.

*

* If @p separator is not found in the string, a single element will be returned in the

* vector containing the entire string.

*

* The separators are removed from the output

*

* @param[in] separator The string separator to split the string on

* @param[in] limit The maximum number of output elements

* @return A vector of strings, each of which is a substring of the string

*

* @ref split_ex

*/

vector<ext_string> split(const string &separator, size_type limit = npos) const

{

vector<ext_string> v;

const_iterator

i = begin(),

last = i;

for (; i != end(); i++)

{

if (string(i, i + separator.length()) == separator)

{

v.push_back(ext_string(last, i));

last = i + separator.length();

if (v.size() >= limit - 1)

{

v.push_back(ext_string(last, end()));

return v;

}

}

}

if (last != i)

v.push_back(ext_string(last, i));

return v;

}

/**

* Convert a string into an integer

*

* Convert the initial portion of a string into a signed integer. Once a non-numeric

* character is reached, the remainder of @p string is ignored and the integer that was

* read returned.

*

* @param s The string to convert

* @return The integer converted from @p string

*/

static long int integer(const string &s)

{

long int retval = 0;

bool neg = false;

for (const_iterator i = s.begin(); i != s.end(); i++)

{

if (i == s.begin())

{

if (*i == '-')

{

neg = true;

continue;

}

else if (*i == '+')

continue;

}

if (*i >= '0' && *i <= '9')

{

retval *= 10;

retval += *i - '0';

}

else

break;

}

if (neg)

retval *= -1;

return retval;

}

/**

* Convert the string to an integer

*

* Convert the initial portion of the string into a signed integer. Once a non-numeric

* character is reached, the remainder of the string is ignored and the integer that had

* been read thus far is returned.

*

* @return The integer converted from the string

*/

long int integer() const

{

return integer(*this);

}

/**

* Split a string into chunks of size @p chunklen. Returns a vector of strings.

*

* Splits a string into chunks of the given size. The final chunk may not fill its

* entire allocated number of characters.

*

* @param[in] chunklen The number of characters per chunk

* @return A vector of strings, each of length <= chunklen

*

* @section chunk_split-ex Example

* @code

* std::ext_string s("abcdefghijk");

* std::vector<std::ext_string> v = s.chunk_split(3);

* std::copy(v.begin(), v.end(), ostream_iterator<std::ext_string>(cout, " "));

*

* abc def ghi jk

* @endcode

*/

vector<ext_string> chunk_split(size_type chunklen) const

{

vector<ext_string> retval;

retval.reserve(size() / chunklen + 1);

size_type count = 0;

const_iterator

i = begin(),

last = i;

for (; i != end(); i++, count++)

{

if (count == chunklen)

{

count = 0;

retval.push_back(ext_string(last, i));

last = i;

}

}

if (last != i)

retval.push_back(ext_string(last, i));

return retval;

}

/**

* Join a sequence of strings by some glue to create a new string

*

* Glue is not added to the end of the string.

*

* @pre [first, last) is a valid range

* @pre InputIterator is a model of STL's Input Iterator

* @pre InputIterator must point to a string type (std::string, std::ext_string, char *)

*

* @param[in] glue The glue to join strings with

* @param[in] first The beginning of the range to join

* @param[in] last The end of the range to join

* @return A string constructed of each element of the range connected together with @p glue

*

* @section join_ex Example

* @code

* std::vector<std::ext_string> v;

* v.push_back("This");

* v.push_back("is");

* v.push_back("a");

* v.push_back("test.");

* std::cout << std::ext_string::join("|", v.begin(), v.end()) << std::endl;

*

* This|is|a|test.

* @endcode

*/

template <class InputIterator>

static ext_string join(const string &glue, InputIterator first, InputIterator last)

{

ext_string retval;

for (; first != last; first++)

{

retval.append(*first);

retval.append(glue);

}

retval.erase(retval.length() - glue.length());

return retval;

}

/**

* Join a sequence of strings by some glue to create a new string

*

* @copydoc join

* @ref join_ex

*/

template <class InputIterator>

static ext_string join(value_type glue, InputIterator first, InputIterator last)

{

ext_string retval;

for (; first != last; first++)

{

retval.append(*first);

retval.append(1, glue);

}

retval.erase(retval.length() - 1);

return retval;

}

/**

* Search for any instances of @p needle and replace them with @p s

*

* @param[in] needle The string to replace

* @param[in] s The replacement string

* @return*this

* @postAll instances of @p needle in the string are replaced with @p s

*

* @section replace-ex Example

* @code

* std::ext_string s("This is a test.");

* s.replace("is", "ere");

* std::cout << s << std::endl;

*

* There ere a test.

* @endcode

*/

ext_string &replace(const string &needle, const string &s)

{

size_type

lastpos = 0,

thispos;

while ((thispos = find(needle, lastpos)) != npos)

{

string::replace(thispos, needle.length(), s);

lastpos = thispos + 1;

}

return *this;

}

/**

* Search of any instances of @p needle and replace them with @p c

*

* @param[in] needle The character to replace

* @param[in] c The replacement character

* @return *this

* @post All instances of @p needle in the string are replaced with @p c

*

* @ref replace-ex

*/

ext_string &replace(value_type needle, value_type c)

{

for (iterator i = begin(); i != end(); i++)

if (*i == needle)

*i = c;

return *this;

}

/**

* Repeat a string @p n times

*

* @param[in] n The number of times to repeat the string

* @return ext_string containing @p n copies of the string

*

* @section repeat-ex Example

* @code

* std::ext_string s("123");

* s = s * 3;

* std::cout << s << std::endl;

*

* 123123123

* @endcode

*/

ext_string operator*(size_type n)

{

ext_string retval;

for (size_type i = 0; i < n; i++)

retval.append(*this);

return retval;

}

/**

* Convert the string to lowercase

*

* @return *this

* @post The string is converted to lowercase

*/

ext_string &tolower()

{

for (iterator i = begin(); i != end(); i++)

if (*i >= 'A' && *i <= 'Z')

*i = (*i) + ('a' - 'A');

return *this;

}

/**

* Convert the string to uppercase

*

* @return *this

* @post The string is converted to uppercase

*/

ext_string &toupper()

{

for (iterator i = begin(); i != end(); i++)

if (*i >= 'a' && *i <= 'z')

*i = (*i) - ('a' - 'A');

return *this;

}

/**

* Count the occurances of @p str in the string.

*

* @return The count of substrings @p str in the string

*/

size_type count(const string &str) const

{

size_type

count = 0,

last = 0,

cur = 0;

while ((cur = find(str, last + 1)) != npos)

{

count++;

last = cur;

}

return count;

}

/**

* Determine if the string is alphanumeric

*

* @return true if the string contains only characters between a-z, A-Z and 0-9 and

* contains at least one character, else false

*/

bool is_alnum() const

{

if (length() == 0)

return false;

for (const_iterator i = begin(); i != end(); i++)

{

if (*i < 'A' || *i > 'Z')

if (*i < '0' || *i > '9')

if (*i < 'a' || *i > 'z')

return false;

}

return true;

}

/**

* Determine if the string is alphabetic only

*

* @return true of the string contains only characters between a-z and A-Z and contains at

* least one character, else false

*/

bool is_alpha() const

{

if (length() == 0)

return false;

for (const_iterator i = begin(); i != end(); i++)

if (*i < 'A' || (*i > 'Z' && (*i < 'a' || *i > 'z')))

return false;

return true;

}

/**

* Determine if the string is numeric only

*

* @return true if the string contains only characters between 0-9 and contains at least

* one character, else false

*/

bool is_numeric() const

{

if (length() == 0)

return false;

for (const_iterator i = begin(); i != end(); i++)

if (*i < '0' || *i > '9')

return false;

return true;

}

/**

* Determine if a string is all lower case

*

* @return true if there is at least one character, and all characters are lowercase

* letters, else false

*/

bool is_lower() const

{

if (length() == 0)

return false;

for (const_iterator i = begin(); i != end(); i++)

if (*i < 'a' || *i < 'z')

return false;

return true;

}

/**

* Determine if a string is all upper case

*

* @return true if there is at least one character, and all characters are uppercase

* letters, else false

*/

bool is_upper() const

{

if (length() == 0)

return false;

for (const_iterator i = begin(); i != end(); i++)

if (*i < 'A' || *i > 'Z')

return false;

return true;

}

/**

* Swap the case of a string

*

* @post Converts all uppercase to lowercase, and all lowercase to uppercase in the string

* @return *this

*/

ext_string &swapcase()

{

for (iterator i = begin(); i != end(); i++)

if (*i >= 'A' && *i <= 'Z')

*i += ('a' - 'A');

else if (*i >= 'a' && *i <= 'z')

*i -= ('a' - 'A');

return *this;

}

};

}

#endif

也可以找到 http://www.gotroot.ca/ext_string/

源文档 <http://www.cppblog.com/mzty/archive/2009/09/16/1721.html>