Chapter 3 C++: String, vector, and array

Chapter 2 introducesBuilt-in types, this chapter introducesAbstract data type library.

- Among them,stringandvectorare the two most important standard library types. The former supportsvariable-length string, The latter represents avariable-length collection.
- Another standard library type isiterator, which is a supporting type of string and vector and is often used to access characters in string and elements in vector.

Chapter 3 Strings, Vectors and Arrays

• Header files should not contain using statements.

Standard library type string

#include using std::string

• Initialization string

• Direct initialization (direct initialization)

• Copy initialization (copy initialization): use the equal sign
  

  string s1;string s2(s1);string s2 = s2;string s3("hiya");string s3 = "hiya";string s4(10, 'c'); //s4的内容是cccccccccc

• Operations on string objects

  1. cout << s2. cin >> s //将string对象读入s，遇到空白停止3. getline(is, s) //从输入流is中读取一行赋给s（换行符被读取了，但被丢弃而没有赋给s），返回is4. s.empty() //s为空返回true，否则返回false5. s.size()6. s[n] //返回s中第n个字符的引用，位置n从0计起 7. s1 + s2 //返回s1和s2连接后的结果8. s1 = s29. s1 == s210. s1 != s211. <, <=, >, >=

• Logical NOT operator (!)

• string::size_type type: The return value type of s.size() is the supporting type of the string class. It is an unsigned type value that can store the size of any string object.

• Processing characters in string objects

• cctype header file: function for judging or processing single characters

  isupper(c) //c是大写字母时为真islower(c)tolower(c) //如果c是大写字母，则输出对于的小写字母；否则原样输出toupper(c)isalpha(c) //c是字母时为真isdigit(c) //c是数字时为真isalnum(c) //c是字母或数字时为真ispunct(c) //c是标点符号时为真isspace(c) //c是空白时为真（即c是空格、横向制表符、纵向制表符、回车符、换行符、进纸符的一种）iscntrl(c) //c是控制字符时为真isgraph(c) //c不是空格但可打印时为真isprint(c) //c是可打印字符时为真（即c是空格或具有可视形式）isxdigit(c) //十六进制数

• Use the C version of the C standard library header file, in the shape of name.h. These files in C are named cname, with the same content, and the names defined in the header file cname belong to the namespace std.

• Range for（range for）statement

for (declaration : expression) statement 例如：string str("some string");//每行输出str中的一个字符for(auto c : str) cout << c <
      
Standard library type vector
      
vector is aclass template(class template). A vector represents a collection of objects, all of which are of the same type. Each object in the collection has a corresponding index, which is used to access the object. Vector is also often calledcontainer(container).
      

       
Definition and initialization of vector objects
      
      
vector v1vector v2(v1)vector v2 = v1vector v3(n, val)vector v4(n)vector v5{a,b,c...}vector v5 = {a,b,c...}
      

       
List initialization vector object
      
      
vector articles = {"a", "an", "the"};
      

       
Add elements to the vector object
The exact number in the vector object is not known until runtime:
string word;vector text;while (cin >> word) { text.push_back(word); }
       

        
Vector objects can grow efficiently: Vector can add elements efficiently and quickly at runtime.
        
If the loop body contains statements that add elements to the vector object, you cannot use the range for loop.
        
push_back: Treat a value as the tail element of the vector object and "push" it to the "tail end (back)" of the vector object.
vector v2;for(int i=0; i != 100; ++1) v2.push_back(i);
       
       
Other vector operations
      
      
v.empty() v.size() v.push_back(t) v[n] //返回v中第n个位置上元素的引用v1 = v2v1 = {a,b,c...}v1 == v2v1 != v2 <, <=, >, >=
      
Iterator iterator
      
A general mechanism: implementation Use the subscript operator to access characters of a string object or elements of a vector object.
      
Similar to pointer types, it provides indirect access to objects.
      

       
begin and end members
//由编译器决定b、e的类型//b表示v的第一个元素，e表示v尾元素的下一个元素auto b = v.begin(), e = v.end(); //b、e类型相同
       

        
The iterator returned by the end member is often called thetail iterator ( off-the-end iterator), or tail iterator for short.
        
If the container is empty, begin and end return both tail iterators.
       
       
Standard containerIterator operator
      
      
*iter 返回迭代器iter所指元素的引用iter->men 解引用iter并获取钙元素的名为mem的成员，等价于（*iter）.mem++iter--iteriter1 == iter2iter1 != iter2
rrree
      

       
# Iterator type
      
      
The standard library with iterators uses iterator and const_iterator to represent the type of iterator:
      

      
//将字符串首字母改成大写string s("some string");if (s.begin() != s.end()) { auto it = s.begin(); *it = toupper(*it); }//将迭代器从一个元素移动到另一个元素，把字符串中第一个单词改为大写//注意，使用的是!=，而不是
      
Reference: C Primer Fifth Edition
      
Chapter 2 IntroductionBuilt-in types, this chapter introducesAbstract data type library
.- Among them,stringandvectorare the two most important standard library types. The former supportsvariable-length strings, and the latter representsVariable-length collection
.- Another standard library type isiterator
, which is a supporting type of string and vector and is often used to access characters in string and elements in vector.
      
Related articles:
      
Chapter 1 C: Function return value, GNU compiler command
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Chapter 2 C: Variables and basic types
      
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