Learning the standard library type of C ++ from scratch (2): Vector class introduction and routine

1. Vector type of the standard library

A vector is a set of objects of the same type.

The data structure of a vector is very similar to an array, allowing efficient and convenient access to a single element.

Vector is a class template)

template <   class Type,    class Allocator = allocator<Type> >class vector

To use vector, the header file must be included.

# Include <vector>

Using STD: vector;

Vector object initialization:

The vector class defines several constructors.

Vector <t> V1;

// The object whose vector storage type is T. The default constructor V1 is null.

Vector <t> V2 (V1); // V2 is a copy of V1.

Vector <t> V3 (n, I); // V3 contains n elements whose values are I.

Vector <t> V4 (N );

// V4 contains N copies of elements whose values are initialized

Common Vector member functions:

Example 1:

C ++ code

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# Include <vector> # Include <iostream> Using namespace STD; Typedef vector <int> intvec; // Void showvec (const intvec & V) //{ // Unsigned int I; // For (I = 0; I <v. Size (); I ++) //{ // Cout <V [I] <""; //} // Cout <Endl; //} // Void showvec (intvec & V) //{ // Intvec: iterator it; // For (IT = V. Begin (); it! = V. End (); ++ it) //{ // Cout <* It <""; //} // // Cout <Endl; //} Void showvec (const intvec & V) { Intvec: const_iterator it; For (IT = V. Begin (); it! = V. End (); ++ it) // All iterators are overloaded! = Operator, but some are not overloaded. { Cout <* It <""; } Cout <Endl; } Int main (void) { Intvec V; V. push_back (1 ); V. push_back (2 ); V. push_back (3 ); Showvec (v ); Return 0; }

Example 2:

C ++ code

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# Include <vector> # Include <iostream> # Include <algorithm> Using namespace STD; Typedef vector <int> intvec; Void showvec (const intvec & V) { Intvec: const_iterator it; For (IT = V. Begin (); it! = V. End (); ++ it) { Cout <* It <""; } Cout <Endl; } Int main (void) { Intvec V; V. push_back (1 ); V. push_back (2 ); V. push_back (3 ); V. push_back (4 ); V. push_back (5 ); V. push_back (3 ); // Cout <v. Back () <Endl; // V. pop_back (); Showvec (v ); // V. Erase (V. Begin () + 2 ); // V. Erase (V. Begin (), V. Begin () + 2 ); V. Erase (remove (V. Begin (), V. End (), 3), V. End ()); Showvec (v ); Return 0; }

Example 3:

C ++ code

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# Include <vector> # Include <iostream> # Include <algorithm> Using namespace STD; Typedef vector <int> intvec; Void showvec (const intvec & V) { Intvec: const_iterator it; For (IT = V. Begin (); it! = V. End (); ++ it) { Cout <* It <""; } Cout <Endl; } Int main (void) { Intvec V; V. push_back (1 ); V. push_back (2 ); V. push_back (3 ); V. push_back (4 ); V. push_back (5 ); V. push_back (3 ); Showvec (v ); // V. Erase (remove (V. Begin (), V. End (), 3), V. End ()); Intvec: iterator it; For (IT = V. Begin (); it! = V. End ();/* ++ it */) { If (* It = 3) { It = V. Erase (it); // erase returns the next element of the currently deleted element. } Else ++ It; } Showvec (v ); Return 0; }

Refer:

C ++ primer version 4
Valid tive C ++ 3rd
C ++ programming specifications