Library: Containers
Does not inherit
A sequence that supports random access iterators
#include <vector>
namespace std {
template <class T, class Allocator = allocator<T> >
class vector;
}
vector is a sequence that supports random access iterators. It also supports amortized constant time insert and erase operations at the end (Insert and erase in the middle take linear time.). Storage management is handled automatically. In vector, iterator is a random access iterator referring to T. const_iterator is a constant random access iterator that returns a const T& when dereferenced. A constructor for iterator and const_iterator is guaranteed. size_type is an unsigned integral type. difference_type is a signed integral type.
Any type used for the template parameter T must provide the following (where T is the type, t is a value of T and u is a const value of T):
Copy constructors T(t) and T(u)
Destructor t.~T()
Address of &t and &u yielding T* and const T*
respectively
Assignment t = a where a is a
(possibly const) value of T
Vectors of bit values, that is boolean 1/0 values, are handled as a special case by the standard library, so that they can be efficiently packed several elements to a word. The operations for a boolean vector, vector<bool>, are a superset of those for an ordinary vector, only the implementation is more efficient.
Two member functions are available to the boolean vector data type. One is flip(), which inverts all the bits of the vector. Boolean vectors also return as reference an internal value that also supports the flip() member function. The other member function specific to vector<bool> is a second form of the swap() function.
namespace std {
template <class T, class Allocator = allocator<T> >
class vector {
public:
// Types
typedef T value_type;
typedef Allocator allocator_type;
typedef typename
Allocator::reference reference;
typedef typename
Allocator::const_reference const_reference;
class iterator;
class const_iterator;
typedef typename
Allocator::size_type size_type;
typedef typename
Allocator::difference_type difference_type;
typedef typename Allocator::pointer pointer;
typedef typename Allocator::const_pointer const_pointer;
typedef typename std::reverse_iterator<iterator>
reverse_iterator;
typedef typename std::reverse_iterator<const iterator>
const_reverse_iterator;
// Construct/Copy/Destroy
explicit vector(const Allocator& = Allocator());
explicit vector(size_type, const Allocator& = Allocator ());
vector(size_type, const T&, const Allocator& = Allocator());
vector(const vector<T, Allocator>&);
template <class InputIterator>
vector(InputIterator, InputIterator,
const Allocator& = Allocator());
vector<T,Allocator>& operator=(const vector<T, Allocator>&);
template <class InputIterator>
void assign(InputIterator start, InputIterator finish);
void assign(size_type, const);
allocator_type get_allocator () const;
// Iterators
iterator begin();
const_iterator begin() const;
iterator end();
const_iterator end() const;
reverse_iterator rbegin();
const_reverse_iterator rbegin() const;
reverse_iterator rend();
const_reverse_iterator rend() const;
// Capacity
size_type size() const;
size_type max_size() const;
void resize(size_type);
void resize(size_type, T);
size_type capacity() const;
bool empty() const;
void reserve(size_type);
// Element Access
reference operator[](size_type);
const_reference operator[](size_type) const;
reference at(size_type);
const_reference at(size_type) const;
reference front();
const_reference front() const;
reference back();
const_reference back() const;
// Modifiers
void push_back(const T&);
void pop_back();
iterator insert(iterator, const T&);
void insert(iterator, size_type, const T&);
template <class InputIterator>
void insert(iterator, InputIterator, InputIterator);
iterator erase(iterator);
iterator erase(iterator, iterator);
void swap(vector<T, Allocator>&);
void clear()
};
// Nonmember Operators
template <class T>
bool operator==(const vector<T,Allocator>&,
const vector <T,Allocator>&);
template <class T>
bool operator!=(const vector<T,Allocator>&,
const vector <T,Allocator>&);
template <class T>
bool operator<(const vector<T,Allocator>&,
const vector<T,Allocator>&);
template <class T>
bool operator>(const vector<T,Allocator>&,
const vector<T,Allocator>&);
template <class T>
bool operator<=(const vector<T,Allocator>&,
const vector<T,Allocator>&);
template <class T>
bool operator>=(const vector<T,Allocator>&,
const vector<T,Allocator>&);
// Specialized Algorithms
template <class T, class Allocator>
void swap (const vector<T,Allocator>&,
const vector<T,Allocator>&);
}
explicit vector(const Allocator& alloc = Allocator());
The default constructor. Creates a vector of length zero. The vector will use the allocator alloc for all storage management.
explicit vector(size_type n);
Creates a vector of length n, containing n copies of the default value for type T. Requires that T have a default constructor. The vector will use the allocator Allocator() for all storage management.
vector(size_type n, const T& value, const Allocator& alloc = Allocator());
Creates a vector of length n, containing n copies of value. The vector will use the allocator alloc for all storage management.
vector(const vector<T, Allocator>& x);
Creates a copy of x.
template <class InputIterator> vector(InputIterator start, InputIterator finish, const Allocator& alloc = Allocator());
Creates a vector of length finish - start, filled with all values obtained by dereferencing the InputIterators on the range [start, finish). The vector will use the allocator alloc for all storage management.
iterator begin();
Returns a random access iterator that points to the first element.
const_iterator begin() const;
Returns a random access const_iterator that points to the first element.
iterator end();
Returns a random access iterator that points to the past-the-end value.
const_iterator end() const;
Returns a random access const_iterator that points to the past-the-end value.
reverse_iterator rbegin();
Returns a random access reverse_iterator that points to the past-the-end value.
const_reverse_iterator rbegin() const;
Returns a random access const_reverse_iterator that points to the past-the-end value.
reverse_iterator rend();
Returns a random access reverse_iterator that points to the first element.
const_reverse_iterator rend() const;
Returns a random access const_reverse_iterator that points to the first element.
vector<T, Allocator>& operator=(const vector<T, Allocator>& x);
Erases all elements in self then inserts into self a copy of each element in x. Returns a reference to self.
allocator_type get_allocator() const;
Returns a copy of the allocator used by self for storage management.
reference operator[](size_type n);
Returns a reference to element n of self. The result can be used as an lvalue. The index n must be between 0 and the size less one.
const_reference operator[](size_type n) const;
Returns a constant reference to element n of self. The index n must be between 0 and the size less one.
template <class InputIterator> void assign(InputIterator start, InputIterator finish);
If InputIterator is an integral type, the function calls assign(size_type(start), value_type (finish)). Otherwise, the function replaces elements in *this with copies of those in the range [start, finish). The function invalidates all iterators and references to elements in *this.
void assign(size_type n, const T& t);
Replaces elements in *this with n copies of t. The function invalidates all iterators and references to elements in *this.
reference at(size_type n);
Returns a reference to element n of self. The result can be used as an lvalue. The index n must be between 0 and the size less one.
const_reference at(size_type) const;
Returns a constant reference to element n of self. The index n must be between 0 and the size less one.
reference back();
Returns a reference to the last element.
const_reference back() const;
Returns a constant reference to the last element.
size_type capacity() const;
Returns the size of the allocated storage, as the number of elements that can be stored.
void clear() ;
Deletes all elements from the vector.
bool empty() const;
Returns true if the size is zero.
iterator erase(iterator position);
Deletes the vector element pointed to by the iterator position. Returns an iterator pointing to the element following the deleted element, or end() if the deleted element was the last one in this vector.
iterator erase(iterator start, iterator finish);
Deletes the vector elements in the range [start, finish). Returns an iterator pointing to the element following the last deleted element, or end() if there were no elements in the deleted range.
void flip();
Flips all the bits in the vector. This member function is only defined for vector<bool>.
reference front();
Returns a reference to the first element.
const_reference front() const;
Returns a constant reference to the first element.
iterator insert(iterator position, const T& x);
Inserts x before position. The return value points to the inserted x.
void insert(iterator position, size_type n, const T& x);
Inserts n copies of x before position.
template <class InputIterator>
void
insert(iterator position, InputIterator start,
InputIterator finish);
Inserts copies of the elements in the range [start, finish) before position.
size_type max_size() const;
Returns size() of the largest possible vector.
void pop_back();
Removes the last element of self.
void push_back(const T& x);
Inserts a copy of x to the end of self.
void reserve(size_type n);
Increases the capacity of self in anticipation of adding new elements. reserve itself does not add any new elements. After a call to reserve, capacity() is greater than or equal to n and subsequent insertions will not cause a reallocation until the size of the vector exceeds n. Reallocation does not occur if n is less than capacity(). If reallocation does occur, then all iterators and references pointing to elements in the vector are invalidated. reserve takes at most linear time in the size of self. reserve throws a length_error exception if n is greater than max_size().
void resize(size_type sz);
Alters the size of self. If the new size (sz) is greater than the current size, then sz-size() instances of the default value of type T are inserted at the end of the vector. If the new size is smaller than the current capacity, then the vector is truncated by erasing size()-sz elements off the end. If sz is equal to capacity then no action is taken.
void resize(size_type sz, T c);
Alters the size of self. If the new size (sz) is greater than the current size, then sz-size() c's are inserted at the end of the vector. If the new size is smaller than the current capacity, then the vector is truncated by erasing size()-sz elements off the end. If sz is equal to capacity then no action is taken.
size_type size() const;
Returns the number of elements.
void swap(vector<T, Allocator>& x);
Exchanges self with x, by swapping all elements.
void swap(reference x, reference y);
Swaps the values of x and y. This is a member function of vector<bool> only.
template <class T, class Allocator>
bool operator==(const vector<T, Allocator>& x,
const vector<T, Allocator>& y);
Returns true if x is the same as y.
template <class T, class Allocator>
bool operator!=(const vector<T, Allocator>& x,
const vector<T, Allocator>& y);
Returns !(x==y).
template <class T>
bool operator<(const vector<T, Allocator>& x,
const vector<T, Allocator>& y);
Returns true if the elements contained in x are lexicographically less than the elements contained in y.
template <class T>
bool operator>(const vector<T, Allocator>& x,
const vector<T, Allocator>& y);
Returns y < x.
template <class T>
bool operator<=(const vector<T, Allocator>& x,
const vector<T, Allocator>& y);
Returns !(y < x).
template <class T>
bool operator>=(const vector<T, Allocator>& x,
const vector<T, Allocator>& y);
Returns !(x < y).
template <class T, class Allocator>void swap(vector <T, Allocator>& a, vector <T, Allocator>& b);
Efficiently swaps the contents of a and b.
//
// vector.cpp
//
#include <vector>
#include <iostream>
typedef std::ostream_iterator<int, char,
std::char_traits<char> >
os_iter_t;
typedef std::vector<int,std::allocator<int> > vector_t;
std::ostream& operator<< (std::ostream& out,
const vector_t& v) {
std::copy(v.begin(), v.end(), os_iter_t(out, " "));
return out;
}
int main () {
// Create a vector of doubles, and one of integers.
vector_t vi;
vector_t::size_type i;
// Insert values before the beginning.
for (i = 0; i < 10; ++i)
vi.insert(vi.begin(), i);
// Print out the vector.
std::cout << vi << std::endl;
// Now let's erase half of the elements.
vector_t::size_type half = vi.size() / 2;
for (i = 0; i < half; ++i)
vi.erase(vi.begin());
// Print it out again.
std::cout << vi << std::endl;
return 0;
}
Program Output:
9 8 7 6 5 4 3 2 1 0 4 3 2 1 0
Member function templates are used in all containers provided by the Standard Template Library. For example, the constructor for vector takes two templatized iterators:
template <class InputIterator>
vector (InputIterator, InputIterator,
const Allocator = Allocator());
vector also has an insert function of this type. These functions, when not restricted by compiler limitations, allow you to use any type of input iterator as arguments. For compilers that do not support this feature we provide substitute functions that allow you to use an iterator obtained from the same type of container as the one you are constructing (or calling a member function on), or you can use a pointer to the type of element you have in the container.
For example, if your compiler does not support member function templates you can construct a vector in the following two ways:
int intarray[10];
vector<int> first_vector(intarray, intarray + 10);
vector<int> second_vector(first_vector.begin(),
first_vector.end());
but not this way:
vector<long> long_vector(first_vector.begin(),first_vector.end());
since the long_vector and first_vector are not the same type.
If your compiler does not support default template parameters, you must supply the Allocator template argument. For instance, you must write :
vector<int, allocator<int> >
instead of :
vector<int>
allocator, Containers, Iterators, lexicographical_compare()
ISO/IEC 14882:1998 -- International Standard for Information Systems -- Programming Language C++, Section 23.2.4