要想使用标准C++中string类，必须要包含
#include <string>// 注意是<string>，不是<string.h>，带.h的是C语言中的头文件
using std::string;
using std::wstring;
或
using namespace std;
构造函数
string();
string( size_type length, char ch );
string( const char *str );
string( const char *str, size_type length );
string( string &str, size_type index, size_type length );
string( input_iterator start, input_iterator end );
字符串的构造函数创建一个新字符串，包括:
• 以length为长度的ch的拷贝（即length个ch）
• 以str为初值 (长度任意),
• 以index为索引开始的子串，长度为length, 或者
• 以从start到end的元素为初值.
例如,
string str1( 5, 'c' );
string str2( "Now is the time..." );
string str3( str2, 11, 4 );
cout << str1 << endl;
cout << str2 << endl;
cout << str3 << endl;
可以用 ==, >, <, >=, <=, and !=比较字符串. 可以用 + 或者 += 操作符连接两个字符串, 并且可以用[]获取特定的字符.
添加文本(append)
语法:
basic_string &append( const basic_string &str );
basic_string &append( const char *str );
basic_string &append( const basic_string &str, size_type index, size_type len );
basic_string &append( const char *str, size_type num );
basic_string &append( size_type num, char ch );
basic_string &append( input_iterator start, input_iterator end );
append() 函数可以完成以下工作:
• 在字符串的末尾添加str,
• 在字符串的末尾添加str的子串,子串以index索引开始，长度为len
• 在字符串的末尾添加str中的num个字符,
• 在字符串的末尾添加num个字符ch,
• 在字符串的末尾添加以迭代器start和end表示的字符序列.
例如以下代码:
string str = "Hello World";
str.append( 10, '!' );
cout << str << endl;
显示
Hello World!!!!!!!!!!
赋值(assign)
语法:
basic_string &assign( const basic_string &str );
basic_string &assign( const char *str );
basic_string &assign( const char *str, size_type num );
basic_string &assign( const basic_string &str, size_type index, size_type len );
basic_string &assign( size_type num, char ch );
函数以下列方式赋值:
• 用str为字符串赋值,
• 用str的开始num个字符为字符串赋值,
• 用str的子串为字符串赋值,子串以index索引开始，长度为len
• 用num个字符ch为字符串赋值.
例如以下代码:
string str1, str2 = "War and Peace";
str1.assign( str2, 4, 3 );
cout << str1 << endl;
显示
and
at
语法:
reference at( size_type index );
at()函数返回一个引用，指向在index位置的字符. 如果index不在字符串范围内, at() 将报告"out of range"错误，并抛出out_of_range异常。 比如下列代码:
string text = "ABCDEF";
char ch = text.at( 2 );
显示字符 'C'.
begin
语法:
iterator begin();
begin()函数返回一个迭代器,指向字符串的第一个元素.
c_str
语法:
const char *c_str();
c_str()函数返回一个指向正规C字符串的指针, 内容与本字符串相同.
容量(capacity)
语法:
size_type capacity();
capacity()函数返回在重新申请更多的空间前字符串可以容纳的字符数. 这个数字至少与 size()一样大.
查找(find)
语法:
size_type find( const basic_string &str, size_type index );
size_type find( const char *str, size_type index );
size_type find( const char *str, size_type index, size_type length );
size_type find( char ch, size_type index );
find()函数:
• 返回str在字符串中第一次出现的位置（从index开始查找）。如果没找到则返回string::npos,
• 返回str在字符串中第一次出现的位置（从index开始查找，长度为length）。如果没找到就返回string::npos,
• 返回字符ch在字符串中第一次出现的位置（从index开始查找）。如果没找到就返回string::npos
例如,
string str1( "Alpha Beta Gamma Delta" );
unsigned int loc = str1.find( "Omega", 0 );
if( loc != string::npos )
cout << "Found Omega at " << loc << endl;
else
cout << "Didn't find Omega" << endl;
插入(insert)
语法:
iterator insert( iterator i, const char &ch );
basic_string &insert( size_type index, const basic_string &str );
basic_string &insert( size_type index, const char *str );
basic_string &insert( size_type index1, const basic_string &str, size_type index2, size_type num );
basic_string &insert( size_type index, const char *str, size_type num );
basic_string &insert( size_type index, size_type num, char ch );
void insert( iterator i, size_type num, const char &ch );
void insert( iterator i, iterator start, iterator end );
insert()函数的功能非常多:
• 在迭代器i表示的位置前面插入一个字符ch,
• 在字符串的位置index插入字符串str,
• 在字符串的位置index插入字符串str的子串(从index2开始，长num个字符),
• 在字符串的位置index插入字符串str的num个字符,
• 在字符串的位置index插入num个字符ch的拷贝,
• 在迭代器i表示的位置前面插入num个字符ch的拷贝,
• 在迭代器i表示的位置前面插入一段字符，从start开始，以end结束.
替换(replace)
语法:
basic_string &replace( size_type index, size_type num, const basic_string &str );
basic_string &replace( size_type index1, size_type num1, const basic_string &str, size_type index2,
size_type num2 );
basic_string &replace( size_type index, size_type num, const char *str );
basic_string &replace( size_type index, size_type num1, const char *str, size_type num2 );
basic_string &replace( size_type index, size_type num1, size_type num2, char ch );
basic_string &replace( iterator start, iterator end, const basic_string &str );
basic_string &replace( iterator start, iterator end, const char *str );
basic_string &replace( iterator start, iterator end, const char *str, size_type num );
basic_string &replace( iterator start, iterator end, size_type num, char ch );
replace()函数:
• 用str中的num个字符替换本字符串中的字符,从index开始
• 用str中的num2个字符（从index2开始）替换本字符串中的字符，从index1开始，最多num1个字符
• 用str中的num个字符（从index开始）替换本字符串中的字符
• 用str中的num2个字符（从index2开始）替换本字符串中的字符，从index1开始，num1个字符
• 用num2个ch字符替换本字符串中的字符，从index开始
• 用str中的字符替换本字符串中的字符,迭代器start和end指示范围
• 用str中的num个字符替换本字符串中的内容,迭代器start和end指示范围，
• 用num个ch字符替换本字符串中的内容，迭代器start和end指示范围.
例如，以下代码显示字符串"They say he carved it himself...find your soul-mate, Homer."
string s = "They say he carved it himself...from a BIGGER spoon";
string s2 = "find your soul-mate, Homer.";
s.replace( 32, s2.length(), s2 );
cout << s << endl;
size
语法:
size_type size();
size()函数返回字符串中现在拥有的字符数。
substr
语法:
basic_string substr( size_type index, size_type num = npos );
substr()返回本字符串的一个子串，从index开始，长num个字符。如果没有指定，将是默认值 string::npos。这样，substr()函数将简单的返回从index开始的剩余的字符串。
例如:
string s("What we have here is a failure to communicate");
string sub = s.substr(21);
cout << "The original string is " << s << endl;
cout << "The substring is " << sub << endl;
显示：
The original string is What we have here is a failure to communicate
The substring is a failure to communicate
交换(swap)
语法:
void swap( basic_string &str );
swap()函数把str和本字符串交换。例如：
string first( "This comes first" );
string second( "And this is second" );
first.swap( second );
cout << first << endl;
cout << second << endl;
显示：
And this is second
This comes first
data
语法:
const char *data();
data()函数返回指向自己的第一个字符的指针.
/* string函数演示 */
/*****************************************
* Copyright (C) 2018 * Ltd. All rights reserved.
*
* File name : string.cpp
* Author : longbin
* Created date: 2018-08-01 19:01:50
* Description :
*
*******************************************/
#include <cstring>
#include <cstdlib>
#include <iostream>
#include <string>
#include <vector>
using namespace std;
#define print(x) cout << __func__ << ">>" << __LINE__ << ">>" << #x << "# " << x << endl
typedef struct {
int type;
int status;
string number;
} CallInfo;
void string_construct()
{
// 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 sequence (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 str0("hello c++ string");
print(str0);
// 1 empty string constructor (default constructor)
// Constructs an empty string, with a length of zero characters.
string str1;
print(str1);
// strcpy(str1, "hello c++ string str1."); // error
// str1 = str0; // OK
// 2 copy constructor
// Constructs a copy of str.
string str2(str0);
print(str2);
// 3 substring constructor
string str3(str0, 3, 5); // 位置+长度
print(str3);
// 4 from c-string
// Copies the null-terminated character sequence (C-string) pointed by s.
string str4("hello c++ string from c-string");
print(str4);
// 5 from buffer
// Copies the first n characters from the array of characters pointed by s.
string str5("hello c++ string from c-string buf", 20); //长度
print(str5);
// 6 fill constructor
// Fills the string with n consecutive copies of character c.
string str6(6, 's');
print(str6);
// 7 range constructor
// Copies the sequence of characters in the range [first,last), in the same order.
string str7(15, 43); // 43 is the ASCII code for '+'
print(str7);
// string_construct>>30>>str0# hello c++ string
// string_construct>>34>>str1#
// string_construct>>41>>str2# hello c++ string
// string_construct>>45>>str3# lo c+
// string_construct>>50>>str4# hello c++ string from c-string
// string_construct>>55>>str5# hello c++ string fro
// string_construct>>60>>str6# ssssss
// string_construct>>65>>str7# +++++++++++++++
}
void string_assign()
{
//string (1) string& operator= (const string& str);
//c-string (2) string& operator= (const char* s);
//character (3) string& operator= (char c);
string s1, s2, s3;
s1 = "string test"; // (2)
s2 = 't'; // (3)
s3 = s1 + s2; // (1)
string s = "hello"; // 1 empty string constructor 2. c-string assign;
// string (1) string& assign (const string& str);
// substring (2) string& assign (const string& str, size_t subpos, size_t sublen);
// c-string (3) string& assign (const char* s);
// buffer (4) string& assign (const char* s, size_t n);
// fill (5) string& assign (size_t n, char c);
// range (6) template <class InputIterator>
// string& assign (InputIterator first, InputIterator last);
string base = "c++ string assign test";
string str;
char str7[] = "hello str7.";
str.assign(base); // (1)
print(str);
str.assign(base, 4, 6); // (2) 位置+长度
print(str);
str.assign("assign from c-string"); // (3)
print(str);
str.assign(str7); // (3)
print(str);
str.assign("assign from buffer", 20); // (4) 长度
print(str); // assign from bufferh
str.assign(8, '*'); // (5)
print(str);
str.assign<int>(10, 0x2D); // (5)
print(str); // ----------
str.assign(base.begin()+4, base.end()-1); // (6)
print(str);
}
void string_clear()
{
return;
// Erases the contents of the string, which becomes an empty string (with a length of 0 characters).
char c;
std::string str;
std::cout << "Please type some lines of text. Enter a dot (.) to finish:\n";
do {
c = std::cin.get();
str += c;
if (c=='\n')
{
std::cout << str;
str.clear();
}
} while (c!='.');
}
void string_c_str()
{
// Get C string equivalent
// Returns a pointer to an array that contains a null-terminated sequence of characters (i.e., a C-string) representing the current value of the string object.
// This array includes the same sequence of characters that make up the value of the string object plus an additional terminating null-character ('\0') at the end.
string str1 = "hello c++ string c_str()";
print(str1);
print(str1.c_str());
char buf[128] = {0};
// strcpy(buf, str1); // error
strcpy(buf, str1.c_str()); // OK
print(buf);
char * cstr = new char[str1.length() + 1];
strcpy(cstr, str1.c_str()); // cstr now contains a c-string copy of str
print(cstr);
}
void string_data()
{
// c_str() 返回的字符串数组以'\0'结尾, data()难以保证，不一定以'\0'结尾，慎用；
// Returns a pointer to an array that contains the same sequence of characters as the characters that make up the value of the string object.
// Accessing the value at data()+size() produces undefined behavior: There are no guarantees that a null character terminates the character sequence pointed by the value returned by this function. See string::c_str for a function that provides such guarantee.
string str = "hello c++ string";
const char *p = "hello c++ string";
if (str.length() == strlen(p))
{
cout << "str and p have the same length." << endl;
if (memcmp(p, str.data(), str.length()))
{
cout << "str and p have the same content." << endl;
}
}
}
void string_at()
{
// Get character in string
// Returns a reference to the character at position pos in the string.
string str1 = "1234567890";
print(str1); //1234567890
print(str1.at(3)); //4
// print(str1.at(str1.length())); // out of range
print(str1[3]);
// print(str1[-1]); //空
}
void string_begin_end()
{
string str1 = "1234567890";
string::iterator it;
for (it = str1.begin(); it != str1.end(); it++)
{
print(*it);
}
print(*str1.begin()); //1
print(*str1.end()); //
print(*(str1.end()-1)); //0
}
void string_append()
{
// string (1) string& append (const string& str);
// substring (2) string& append (const string& str, size_t subpos, size_t sublen);
// c-string (3) string& append (const char* s);
// buffer (4) string& append (const char* s, size_t n);
// fill (5) string& append (size_t n, char c);
// range (6) template <class InputIterator>
// string& append (InputIterator first, InputIterator last);
string str1 = "hello ";
string str2 = "c++ ";
print(str1);
print(str2);
str1.append(str2); // (1)
cout << "str1.append(str2): " << str1 << endl; //hello c++
str1.append(str2, 1, 2); // (2)
cout << "str1.append(str2, 1, 2): " << str1 << endl; //hello c++ ++
str1.append("good"); // (3)
cout << "str1.append(\"good\"): " << str1 << endl; //hello c++ ++good
str1.append("good", 3); // (4)
cout << "str1.append(\"good\", 3): " << str1 << endl;//hello c++ ++goodgoo
str1.append(5, '-'); // (5)
cout << "str1.append(5, '-'): " << str1 << endl; //hello c++ ++goodgoo-----
str1.append(str2.begin()+1, str2.end()-1); // (6)
cout << "str1.append(str2.begin()+1, str2.end()-1): " << str1 << endl; //hello c++ ++goodgoo-----++
}
void string_replace()
{
// string (1) string& replace (size_t pos, size_t len, const string& str);
// string& replace (iterator i1, iterator i2, const string& str);
// substring (2) string& replace (size_t pos, size_t len, const string& str, size_t subpos, size_t sublen);
// c-string (3) string& replace (size_t pos, size_t len, const char* s);
// string& replace (iterator i1, iterator i2, const char* s);
// buffer (4) string& replace (size_t pos, size_t len, const char* s, size_t n);
// string& replace (iterator i1, iterator i2, const char* s, size_t n);
// fill (5) string& replace (size_t pos, size_t len, size_t n, char c);
// string& replace (iterator i1, iterator i2, size_t n, char c);
// range (6) template <class InputIterator>
// string& replace (iterator i1, iterator i2, InputIterator first, InputIterator last);
// 0123456789*23456789*123
std::string base = "this is a test string.";
std::string str2 = "n example";
std::string str3 = "sample phrase";
std::string str4 = "useful.";
// replace signatures used in the same order as described above:
// 位置参数的前2个表示替换范围,后面是使用的字符串
// Using positions: 0123456789*123456789*12345
std::string str = base; // "this is a test string."
str.replace(9, 5, str2); // "this is an example string." (1) str[9:+5] <-- str2;
str.replace(19, 6, str3, 7, 6); // "this is an example phrase." (2) str[19:+6] <-- str3[7:+6];
str.replace(8, 10, "just a"); // "this is just a phrase." (3) str[8:+10] <-- "just a";
str.replace(8, 6, "a shorty", 7); // "this is a short phrase." (4) str[8:+6] <-- "a shorty"[:+7];
str.replace(22, 1, 3, '!'); // "this is a short phrase!!!" (5) str[22:+1] <-- 3*'!';
// Using iterators: 0123456789*123456789*
str.replace(str.begin(), str.end()-3, str3); // "sample phrase!!!" (1)
str.replace(str.begin(), str.begin()+6, "replace"); // "replace phrase!!!" (3)
str.replace(str.begin()+8, str.begin()+14,"is coolness", 7); // "replace is cool!!!" (4)
str.replace(str.begin()+12, str.end()-4, 4, 'o'); // "replace is cooool!!!" (5)
str.replace(str.begin()+11, str.end(), str4.begin(), str4.end());// "replace is useful." (6)
print(str); // replace is useful.
}
void string_capacity()
{
// Return size of allocated storage
// Returns the size of the storage space currently allocated for the string, expressed in terms of bytes.
// The capacity of a string can be explicitly altered by calling member reserve.
string str1 = "hello c++ string.";
print(str1.length());
print(str1.size()); // <==> length()
print(str1.capacity());
print(str1.max_size());
str1 = "0123456789*123456789*123456789*123456789";
print(str1.length()); //40
print(str1.capacity()); //40
str1 = "hello c++";
print(str1.length()); //9
print(str1.capacity()); //40
CallInfo info;
// c++ string 作为结构体时, 需要使用new而不是malloc来申请空间
info.type = 5;
info.status = 6;
info.number = "123456789012";
print(sizeof(info)); //16
string str_hello = "hello world";
print(str_hello);
print(sizeof(str_hello)); //8
string crash = "hello";
print(crash);
crash.clear();
print(crash);
// 用sizeof来返回类型以及静态分配的对象/结构/数组所占的空间,返回值跟对象/结构/数组所存储的内容没有关系;
// 当参数分别如下时,sizeof返回的值表示的含义如下:
// 数组——编译时分配的数组空间大小;
// 指针——存储该指针所用的空间大小(存储该指针的地址的长度，是长整型，应该为4);
// 类型——该类型所占的空间大小;
// 对象——对象的实际占用空间大小;
// 函数——函数的返回类型所占的空间大小。函数的返回类型不能是void;
char arr0[20] = "hello arr0";
char arr1[] = "hello arr1";
char *pstr = new char[20];
strcpy(pstr, arr0);
//sizeof不是一个函数,sizeof可以不加括号;sizeof更像一个特殊的宏,它是在编译阶段求值的;
//注意sizeof()中的语句不会生效;
//sizeof(string)和字符串的长度是无关的,在一个系统中所有的sizeof(string)是一个固定值;
//这个和编译器相关,string字符串是存储在堆上,这个属于动态分配的空间;
string sstr = "hello sstr";
print(sizeof(arr0)); //20
print(sizeof(arr1)); //11
print(sizeof(pstr)); //8
print(sizeof(sstr)); //8
print(sstr);
sizeof(sstr = "sizeof expr");
print(sstr); //"hello sstr"
}
void string_length()
{
// Return length of string
// Returns the length of the string, in terms of bytes.
// 0123456789*12345
string str("hello c++ string");
print(str.length()); //16
}
void string_size()
{
// Return length of string
// Returns the length of the string, in terms of bytes.
// 0123456789*12345
string str("hello c++ string");
print(str.size()); //16
// length是因为沿用C语言的习惯而保留下来的,string类最初只有length;
// 引入STL之后,为了兼容又加入了size,它是作为STL容器的属性存在的,便于符合STL的接口规则,以便用于STL的算法;
// string类的size()/length()方法返回的是字节数,不管是否有汉字;
}
void string_erase()
{
// sequence (1) string& erase (size_t pos = 0, size_t len = npos);
// Erases the portion of the string value that begins at the character position pos and spans len characters;
// or until the end of the string, if either the content is too short or if len is string::npos.
// Notice that the default argument erases all characters in the string (like member function clear).
// character (2) iterator erase (iterator p);
// Erases the character pointed by p.
// range (3) iterator erase (iterator first, iterator last);
// Erases the sequence of characters in the range [first,last).
// 0123456789*123456789*123
string str("hello c++ string example");
print(str);
str.erase(17, 7); // (1)
print(str); //hello c++ string
str.erase(str.begin()+10); // (2) Erases the character pointed by p.
print(str); //hello c++ tring
str.erase(str.begin()+6, str.begin()+8); // (3)
print(str); //hello + tring
str.erase(); // (1) <==> str.clear();
print(str); //
}
void string_insert()
{
// string (1) string& insert (size_t pos, const string& str);
// substring (2) string& insert (size_t pos, const string& str, size_t subpos, size_t sublen);
// c-string (3) string& insert (size_t pos, const char* s);
// buffer (4) string& insert (size_t pos, const char* s, size_t n);
// fill (5) string& insert (size_t pos, size_t n, char c);
// void insert (iterator p, size_t n, char c);
// single character (6) iterator insert (iterator p, char c);
// range (7) template <class InputIterator>
// void insert (iterator p, InputIterator first, InputIterator last);
// 0123456789*123
std::string str = "to be question";
std::string str2 = "the ";
std::string str3 = "or not to be";
std::string::iterator it;
// used in the same order as described above:
// 0123456789*123456789*123456789
str.insert(6, str2); // (1) // to be the question
print(str);
str.insert(6, str3, 3, 4); // (2) // to be not the question
str.insert(10, "that is cool", 8); // (4) // to be not that is the question
str.insert(10, "to be "); // (3) // to be not to be that is the question
str.insert(15, 1, ':'); // (5) // to be not to be: that is the question
it = str.insert(str.begin()+5, ','); // (6) // to be, not to be: that is the question
str.insert(str.end(), 3, '.'); // (5) // to be, not to be: that is the question...
str.insert(it+2, str3.begin(), str3.begin()+3); // (7) // to be, or not to be: that is the question...
print(str);
}
void string_empty()
{
// Test if string is empty
// Returns whether the string is empty (i.e. whether its length is 0).
string str0 = "hello c++ string";
string str1 = str0;
string str2 = "";
string str3;
print(str0.empty()); // 0
print(str1.empty()); // 0
print(str2.empty()); // 1
print(str3.empty()); // 1
str0.erase();
print(str0.empty()); // 1
str1.clear();
print(str1.empty()); // 1
}
void string_compare()
{
// Compare strings
//Compares the value of the string object (or a substring) to the sequence of characters specified by its arguments.
// string (1) int compare (const string& str) const;
// substrings (2) int compare (size_t pos, size_t len, const string& str) const;
// int compare (size_t pos, size_t len, const string& str, size_t subpos, size_t sublen) const;
// c-string (3) int compare (const char* s) const;
// int compare (size_t pos, size_t len, const char* s) const;
// buffer (4) int compare (size_t pos, size_t len, const char* s, size_t n) const;
string str0 = "hello c++ string 0";
string str1 = "hello c++ string 1";
string str2 = "hello c++ string 2";
string str3 = "hello c++ string 0";
string str4 = "c++";
print(str1.compare(str2)); // (1) // <0
print(str0.compare(str3)); // (1) // ==0
print(str2.compare(str1)); // (1) // >0
print(str0.compare(6, 3, str4)); // (2) // ==0
print(str0.compare(6, 3, str1, 6, 3)); // (2) // ==0
print(str0.compare("hello c++ string 0")); // (3) // ==0
print(str0.compare(6, 3, "c++")); // (3) // ==0
print(str0.compare(6, 3, "c++ good", 3)); // (4) // ==0
}
void string_copy()
{
// size_t copy (char* s, size_t len, size_t pos = 0) const;
// Copy sequence of characters from string
// The function does not append a null character at the end of the copied content.
char buf[128] = "9876543210";
string str1 = "0123456789";
print(str1);
size_t size = str1.copy(buf, 4, 3); //str len index
print(buf); // 3456543210
print(strlen(buf)); // 10
print(size); // 4
buf[size] = '\0';
print(buf); // 3456
print(strlen(buf)); // 4
// std::copy()
// template <class InputIterator, class OutputIterator>
// OutputIterator copy (InputIterator first, InputIterator last, OutputIterator result);
// Copy range of elements
// Copies the elements in the range [first,last) into the range beginning at result.]
string str = "9876543210";
std::copy(str1.begin()+3, str1.begin()+7, str.begin()); // [3, 7); // no '\0' end;
print(str); // 3456543210
print(strlen(str.data())); // 10
print(str.length()); // 10
str.assign(str1, 3, 4);
print(str); // 3456
print(strlen(str.data())); // 4
print(str.length()); // 4
}
void string_find()
{
// Find content in string
// Searches the string for the first occurrence of the sequence specified by its arguments.
// Return Vaulue:
// The position of the first character of the first match.
// If no matches were found, the function returns string::npos.
// 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;
string str = "hello c++ string find c++";
string f1 = "c++";
size_t fpos = 0;
fpos = str.find(f1); // (1)
cout << "first c++ found at: " << fpos << endl;
fpos = str.find(f1, fpos+1); // (1)
cout << "second c++ found at: " << fpos << endl;
fpos = str.find("c++"); // (2)
cout << "c++ found at: " << fpos << endl;
fpos = str.find("c++", 2); // (2)
cout << "c++ found at: " << fpos << endl;
fpos = str.find("c++ good", 7, 3); // (3) //str[pos:] "c++ good"[:3]
cout << "c++ found at: " << fpos << endl;// 22 // found "c++" from "hello c(++ string find c++)"
fpos = str.find('+', 15); // (4)
cout << "+ found at: " << fpos << endl; // 23 // found '+' from "hello c++ strin(g find c++)"
}
void string_substr()
{
// string substr (size_t pos = 0, size_t len = npos) const;
// Generate substring
// Returns a newly constructed string object with its value initialized to a copy of a substring of this object.
string str1 = "hello c++ string substr.";
string sub;
size_t pos;
pos = str1.find("c++", 0);
sub = str1.substr(pos);
print(sub);
sub = str1.substr(pos, 3);
print(sub);
string info(17, '6');
size_t step = 6;
// string info(20, '6');
// size_t step = 20;
for (pos = 0; pos < info.length(); pos+=step)
{
cout << pos << ": " << info.substr(pos, step) << endl;
}
}
vector<string> split(string &src, const string & delim)
{
vector<string> lst;
size_t pos1 = 0;
size_t pos2 = 0;
string sstr;
// print(src);
// print(delim);
while (string::npos != (pos2 = src.find(delim, pos1)))
{
sstr = src.substr(pos1, pos2-pos1);
// print(sstr);
lst.push_back(sstr);
pos1 = pos2 + delim.size();
}
if (src.length() != pos1)
{
lst.push_back(src.substr(pos1));
}
return lst;
}
template <class T>
string join(T& val, string delim)
{
string str;
string ele;
typename T::iterator it;
for (it = val.begin(); it != val.end(); it++)
{
ele = *it;
str.append(ele);
if (it != val.end()-1)
{
str.append(delim);
}
}
return str;
}
string strip(string str, const string delim="")
{
string chr;
string::iterator it;
string sp = delim;
if (0 == sp.length())
{
//print(sp);
sp = " \t\n\v\f\r";
}
while (string::npos != sp.find(str.at(0)))
{
str.erase(0, 1);
}
while (string::npos != sp.find(str.at(str.length()-1)))
{
str.erase(str.length()-1, 1);
}
return str;
}
string mask(const string &src, int pos, int masklen)
{
string ret = src;
string mask = "";
int length = (int)ret.length();
int replen = 0;
if (pos < 0)
{
// mask from tail
pos = length + pos;
}
if ((pos < 0) || (length <= pos))
{
// pos is out of range
return ret;
}
if (masklen >= 0)
{
replen = ((length - pos) > masklen) ? masklen : (length - pos);
}
else
{
// mask from tail
replen = ((pos + 1) > -masklen) ? -masklen : (pos + 1);
pos = (pos + 1) - replen;
}
if ((pos >= 0) && (pos < length))
{
// cout << "true" << endl;
mask.assign(replen, '*');
ret = ret.replace(pos, replen, mask);
}
return ret;
}
int main() {
string split_line(30, '#');
cout << split_line << endl;
string_construct();
string_assign();
string_clear();
string_c_str();
string_data();
string_at();
string_begin_end();
string_append();
string_erase();
string_insert();
string_replace();
string_capacity();
string_length();
string_size();
string_empty();
string_compare();
string_copy();
string_find();
string_substr();
// extended function
// join(str, delim);
vector<string> vec(4, "good");
print(join(vec, "/"));
string jstr(6, '0');
print(join(jstr, "-"));
// split(str, delim);
string str = "/usr/local/bin/python";
vector<string> vt = split(str, "/");
vector<string>::iterator it;
for (it = vt.begin(); it != vt.end(); it++)
{
print(*it);
}
// strip(str, chars);
str = " 0hello good 0 ";
str = strip(str, "0 ");
print(str);
print(str.length());
// strip(str);
str = " 0hello good 0 ";
str = strip(str);
print(str);
print(str.length());
// mask
string test = "01234567890";
print(test);
print(mask(test, 1, 3)); //0***4567890
print(mask(test, 0, 4)); //****4567890
print(mask(test, -1, -3)); //01234567***
cout << split_line << endl;
return 0;
}
参考资料
https://blog.csdn.net/tengfei461807914/article/details/52203202
https://www.cnblogs.com/aminxu/p/4686320.html