STL Overview

昵称7737891 2011-09-17

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Vector

Vectors are composed of a single block of sequential memory, just like C vectors (see diagram).
Memory extended in multi-object blocks.
Memory is freed when the vector object is destroyed.
Use when objects are inserted/removed primarily at the end.
Inefficiency: Overflow condition can cause a complete copy.
Type requirements for T: T(); T(const T&); ~T(); T& operator=(const T&);

example:

#include < iostream.h >
#include < vector.h >
void print (vector < double >& vector_)
{
for (int i = 0; i < vector_.size (); i++)
cout << vector_[i] << " ";
cout << endl;
}
int main ()
{
vector < double > v1; // Empty vector of doubles.
v1.push_back (32.1);
v1.push_back (40.5);
vector< double > v2; // Another empty vector of doubles.
v2.push_back (3.56);
cout << "v1 = ";
print (v1);
cout << "v2 = ";
print (v2);
v1.swap (v2); // Swap the vector's contents.
cout << "v1 = ";
print (v1);
cout << "v2 = ";
print (v2);
v2 = v1; // Assign one vector to another.
cout << "v2 = ";
print (v2);
return 0;
}

output:


v1 = 32.1 40.5
v2 = 3.56
v1 = 3.56
v2 = 32.1 40.5
v2 = 3.56

deque

Deques are composed of fixed-size multi-object blocks of memory with a "map" block (see diagram).
Memory is freed when the vector object is destroyed.
Use when objects are inserted/removed primarily at the end or the beginning.
Inefficiency: no complete copies, but operator[] is a bit slower.
Type requirements for T: T(); T(const T&); ~T(); T& operator=(const T&);

example:

#include < iostream.h >
#include < deque.h >
int main ()
{
deque< int > d;
d.push_back (4); // Add after end.
d.push_back (9);
d.push_back (16);
d.push_front (1); // Insert at beginning.
for (int i = 0; i < d.size (); i++)
cout << "d[" << i << "] = " << d[i] << endl;
cout << endl;
d.pop_front (); // Erase first element.
d[2] = 25; // Replace last element.
for (i = 0; i < d.size (); i++)
cout << "d[" << i << "] = " << d[i] << endl;
return 0;
}

output:


d[0] = 1
d[1] = 4
d[2] = 9
d[3] = 16
d[0] = 4
d[1] = 9
d[2] = 25

list

Lists are composed prev-object-next blocks (see diagram).
Objects are allocated from same-type static private pool. (see diagram)
Memory isn't freed until every member of the class is destroyed.
Use when objects are inserted/removed anywhere in the list.
No operator[].
Inefficiency: highest overhead.
Type requirements for T: T(); T(const T&); ~T(); T& operator=(const T&); T* operator&(); int operator < (const T&, const T&); int operator==(const T&, const T&);

example:

#include < iostream.h >
#include < list.h >
int array1 [] = { 9, 16, 36 };
int array2 [] = { 1, 4 };
int main ()
{
list< int > l1 (array1, array1 + 3);
list< int > l2 (array2, array2 + 2);
list< int >::iterator i1 = l1.begin ();
l1.splice (i1, l2);
list< int >::iterator i2 = l1.begin ();
while (i2 != l1.end ())
cout << *i2++ << endl;
return 0;
}

output: