stringクラスの使い方

12209 ワード
C/C++
コンストラクション関数:
  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);//注意位置情報は定数であり、反復器ではありません.  std::string s4 ("A character sequence");   std::string s5 ("Another character sequence", 12);   std::string s6a (10, 'x');   std::string s6b (10, 42);      //42 is the ASCII code for '*'   std::string s7 (s0.begin(), s0.begin()+7); 
s1: 
s2: Initial string
s3: str
s4: A character sequence
s5: Another char
s6a: xxxxxxxxxx
s6b: **********
s7: Initial

代入演算子のリロード(operator=):
string (1) 
string& operator= (const string& str);

c-string (2) 
string& operator= (const char* s);

character (3) 
string& operator= (char c);

initializer list (4) 
string& operator= (initializer_list il);

move (5) 
string& operator= (string&& str) noexcept;
  std::string str1, str2, str3;
  str1 = "Test string: ";   // c-string
  str2 = 'x';               // single character
  str3 = str1 + str2;       // string

反復器:
vectorの反復器と同じように、逆方向と定数反復器です.
 
容量:
size,length,max_size,resize,capacity,reserve,clear,empty,shrink_to_fit;
vectorに比べてlengthメソッドが1つ増え、sizeと全く同じです.
 
要素アクセス:
operator[], at, back, front
str.back()とstr.frontは左の値で、等号の左側でも右側でもかまいません.
 
変更:
operator+=(非メンバー関数operator+との違いに注意)
  std::string name ("John");
  std::string family ("Smith");
  name += " K. ";         // c-string
  name += family;         // string
  name += '
';           // character

append(末尾に追加文字を追加することで元stringを拡張)
  std::string str;
  std::string str2="Writing ";
  std::string str3="print 10 and then 5 more";

  // used in the same order as described above:
  str.append(str2);                       // "Writing "
  str.append(str3,6,3);                   // "10 "
  str.append("dots are cool",5);          // "dots "
  str.append("here: ");                   // "here: "
  str.append(10u,'.');                    // ".........."
  str.append(str3.begin()+8,str3.end());  // " and then 5 more"
  str.append(5,0x2E);                // "....."

  std::cout << str << '
';Writing 10 dots here: .......... and then 5 more.....

push_back 尾部添加一个字符，只接受char类型。pop_back删除字符串最后一个char.

void push_back (char c);
void pop_back();

 
assign割り当ては、通常、空string Aを定義し、assignを介してAを文字列に割り当てます.
 
Insert関数が多く、入力パラメータはpos位置情報であってもよいし、反復器であってもよい.戻りパラメータは反復器でもstringでもよい.
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);
iterator insert (const_iterator p, size_t n, char c);

single character (6) 
iterator insert (const_iterator p, char c);

range (7) 
template 
iterator insert (iterator p, InputIterator first, InputIterator last);

initializer list (8) 
 string& insert (const_iterator p, initializer_list il);
  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:
  str.insert(6,str2);                 // to be (the )question
  str.insert(6,str3,3,4);             // to be (not )the question
  str.insert(10,"that is cool",8);    // to be not (that is )the question
  str.insert(10,"to be ");            // to be not (to be )that is the question
  str.insert(15,1,':');               // to be not to be(:) that is the question
  it = str.insert(str.begin()+5,','); // to be(,) not to be: that is the question
  str.insert (str.end(),3,'.');       // to be, not to be: that is the question(...)
  str.insert (it+2,str3.begin(),str3.begin()+3); // (or )

  std::cout << str << '
';

eraseは反復器パラメータを受け入れて反復器パラメータを返し、pos位置パラメータを受け入れて修正後stringを返します.
sequence (1) 
 string& erase (size_t pos = 0, size_t len = npos);

character (2) 
iterator erase (const_iterator p);

range (3) 
iterator erase (const_iterator first, const_iterator last);
  std::string str ("This is an example sentence.");
  std::cout << str << '
';
                                           // "This is an example sentence."
  str.erase (10,8);                        //            ^^^^^^^^
  std::cout << str << '
';
                                           // "This is an sentence."
  str.erase (str.begin()+9);               //           ^
  std::cout << str << '
';
                                           // "This is a sentence."
  str.erase (str.begin()+5, str.end()-9);  //       ^^^^^
  std::cout << str << '
';

replace置換(戻り値はstring&)
  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:

  // 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.replace(19,6,str3,7,6);     // "this is an example phrase." (2)
  str.replace(8,10,"just a");     // "this is just a phrase."     (3)
  str.replace(8,6,"a shorty",7);  // "this is a short phrase."    (4)
  str.replace(22,1,3,'!');        // "this is a short phrase!!!"  (5)

  // 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)

swap交換
str1.swap(str2);
 
文字列アクション:
c_str  stringからC型文字列への変換を提供
const char* c_str() const noexcept;

copyは、現在のstringの部分を宛先にコピーします.
  char buffer[20];
  std::string str ("Test string...");
  std::size_t length = str.copy(buffer,6,5);
  buffer[length]='\0';
  std::cout << "buffer contains: " << buffer << '
';

findは文字列または文字を検索し、検索した場所を返します.注意std::string::npos(デフォルト-1)この定数は見つかりません.rfind逆検索.
  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 << '
';

  found=str.find("needles are small",found+1,6);
  if (found!=std::string::npos)
    std::cout << "second 'needle' found at: " << found << '
';

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

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

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

find_first_of stringまたはcharを受け入れ、stringの最初の文字を見つけ、入力パラメータのいずれかのcharに一致する.
find_last_of最後に一致する位置を見つけます.
find_first_not_of
find_last_not_of 
  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);
  }


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

 
substr stringの文字列を取り出します.pos位置パラメータを受け入れます.1番目は位置を表し、2番目は長さを表し、デフォルトのパラメータがあります.
string substr (size_t pos = 0, size_t len = npos) const;
  std::string str="We think in generalities, but we live in details.";
                                           // (quoting Alfred N. Whitehead)

  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

compare比較stringとそのパラメータ文字シーケンスが等しいかどうか.戻り値はint判定が0に等しいか否かである.
  std::string str1 ("green apple");
  std::string str2 ("red apple");

  if (str1.compare(str2) != 0)
    std::cout << str1 << " is not " << str2 << '
';

  if (str1.compare(6,5,"apple") == 0)
    std::cout << "still, " << str1 << " is an apple
";

  if (str2.compare(str2.size()-5,5,"apple") == 0)
    std::cout << "and " << str2 << " is also an apple
";

  if (str1.compare(6,5,str2,4,5) == 0)
    std::cout << "therefore, both are apples
";

 
非メンバー関数:
operator+ 
  std::string firstlevel ("com");
  std::string secondlevel ("cplusplus");
  std::string scheme ("http://");
  std::string hostname;
  std::string url;

  hostname = "www." + secondlevel + '.' + firstlevel;
  url = scheme + hostname;

==   !=      >= 
  std::string foo = "alpha";
  std::string bar = "beta";

  if (foo==bar) std::cout << "foo and bar are equal
";
  if (foo!=bar) std::cout << "foo and bar are not equal
";
  if (foo< bar) std::cout << "foo is less than bar
";
  if (foo> bar) std::cout << "foo is greater than bar
";
  if (foo<=bar) std::cout << "foo is less than or equal to bar
";
  if (foo>=bar) std::cout << "foo is greater than or equal to bar
";

swap交換
swap(str1, str2);
 
<>  入出力リロード
 
getline   注意cin.get(name,20)とcin.getline(name,20)を区別して改行を破棄します.
  std::string name;
  std::cout << "Please, enter your full name: ";
  std::getline (std::cin,name);
  std::cout << "Hello, " << name << "!
";
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