Chapter III C + +: string strings, vector vectors and arrays

Chapter 2 introduces built-in types. This chapter introduces abstract data type libraries.

-Among them, string and vector are the two most important standard library types. The former supports variable-length strings and the latter represents variable-length collections.
-Another standard library type is the iterator, which is a matching type of string and vector. It is often used to access characters in strings and elements in vectors.

Chapter 3 Strings, Vectors, and Arrays
The header file should not contain a using statement.

Standard library type string
#include <string> using std :: string
Initialization string

Direct 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'); // The content of s4 is cccccccccc
Operations on string objects

1. cout << s2. Cin >> s // Read the string object into s and stop when it encounters a blank 3. getline (is, s) // Read a line from the input stream is and assign it to s (newline characters are read Taken, but discarded without assigning to s), returns is4. S.empty () // returns true if s is empty, otherwise returns false5. S.size () 6. S [n] // returns the first in s n character quotes, position n starts from 0
7. s1 + s2 // Return the result of connecting s1 and s2 8. s1 = s29. S1 == s210. S1! = S211. <, <=,>,> =
Logical NOT operator (!)

string :: size_type Type: The return value type of s.size () is a matching type of the string class. It is an unsigned value that can hold the size of any string object.

Handling characters in string objects
cctype header file: functions for judging or processing single characters

isupper (c) // true if c is an uppercase letter islower (c) tolower (c) // if c is an uppercase letter, the corresponding lowercase letter is output; otherwise toupper (c) isalpha (c) // c is output as is True when it is a letter isdigit (c) // true when c is a number isalnum (c) // true when c is a letter or number ispunct (c) // true when c is punctuation isspace (c) // true if c is blank (that is, c is a type of space, horizontal tab, vertical tab, carriage return, line feed, or paper feed) iscntrl (c) // true if c is a control character isgraph (c) // c is not a space but is true when it is printable isprint (c) // c is true when it is a printable character (ie c is a space or has a visual form) isxdigit (c) // Hexadecimal number
Use the C ++ version of the C standard library header files of the form name.h. In C ++++ these files are named cname with the same contents, and the names defined in the header file cname belong to the namespace std.

Range for statement

for (declaration: expression)
    statement

For example: string str ("some string"); // Each line outputs a character in str for (auto c: str) cout << c << endl;
Standard library type vector
vector is a class template. A vector represents a collection of objects, where all objects are of the same type. Each object in the collection has a corresponding index, which is used to access the object. Vectors are often called containers.

Define and initialize vector objects

vector <T> v1vector <T> v2 (v1) vector <T> v2 = v1vector <T> v3 (n, val) vector <T> v4 (n) vector <T> v5 {a, b, c ... } vector <T> v5 = {a, b, c ...}
List initialization vector object

vector <string> articles = {"a", "an", "the"};
Add elements to a vector object
The exact number of vector objects is known at runtime:

string word; vector <string> text; while (cin >> word) {
    text.push_back (word);
}
Vector objects can grow efficiently: vectors can add elements quickly and efficiently at runtime.

If the body of the loop contains a statement that adds elements to a vector object, you cannot use a ++ scope for ++ loop.

push_back: "Push" a value as the tail element of the vector object "back" of the vector object.

vector <int> 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] // Returns a reference to the element at the nth position in v v1 = v2v1 = (a, b, c ...) v1 == v2v1! = v2
<, <=,>,> =
Iterator
A general mechanism: implement the use of subscript operators to access characters of string objects or elements of vector objects.

Like pointer types, it provides indirect access to objects.

begin and end members
// The compiler determines the type of b and e // b represents the first element of v, and e represents the next element of the v tail element auto b = v.begin (), e = v.end (); // b, e type are the same
The iterator returned by the end member is often called an off-the-end iterator, or simply an iterator.

If the container is empty, both begin and end return iterators.

Standard container iterator operator
* iter returns a reference to the element pointed to by the iterator iter-> men dereferences iter and gets the member of the calcium element named mem, which is equivalent to (* iter) .mem ++ iter--iteriter1 == iter2iter1! = iter2
// Change the first letter of the string to uppercase string s ("some string"); if (s.begin ()! = S.end ()) {auto it = s.begin ();
    * it = toupper (* it);
} // Move the iterator from one element to another, and change the first word in the string to uppercase // Note that you use! = Instead of <for (auto it = s.begin (); it! = s.end () &&! isspace (* it); ++ it)
    * it = toupper (* it);
#### Iterator Type

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

vector <int> :: iterator it; // it can read and write elements in vector <int> string :: iterator it2; // it2 can read and write characters in string object vector <int> :: const_iterator it3; // it3 can only read elements, cannot write elements string :: const_iterator it4; // it4 can only read characters, cannot write characters
Reference: C ++ Primer Fifth Edition

Chapter 2 introduces built-in types. This chapter introduces abstract data type libraries.
-Among them, string and vector are the two most important standard library types. The former supports variable-length strings and the latter represents variable-length collections.
-Another standard library type is the iterator, which is a matching type of string and vector. It is often used to access characters in strings and elements in vectors.

related articles:

Chapter C ++: Function Return Values, GNU Compiler Commands

Chapter 2 C ++: Variables and Basic Types