CSE 40872 Lecture 004

Standard Template Library (STL)

C++ library of commonly used data structures and algorithms.

• Containers:

  • Sequence: vector, deque, list, string, stack
  • Associative: set, map

• Algorithms:

  • Search: find, count, search, binary_search
  • Sort: sort
  • Heap: make_heap, sort_heap

STL Containers

Collection of elements of a particular type.

vector<int>         mVector;
map<string, int>    mMap;
list< set<double> > mListOfSets;

Templates (i.e ``<Type>``) allow customization and optimization of data structures.

Common Methods

• push_back(item): Append item to the back of the container.

mVector.push_back(12345);

• clear(): Remove all items from container.

mVector.clear();

• size(): Return size/length of container.

mVector.size();

Iterators

• To iterate or traverse through containers, STL provides iterators.

  • Can be thought of as references or pointers to items in the container.
  • Container::iterator or Container::reverse_iterator.

• STL containers have 4 special iterators: begin(), end(), rbegin(), rend().

• Modifying the container may invalidate iterators.

Used throughout STL, so get used to them.

Example

Print items in a vector:

for (int i = 0; i < mVector.size(); i++)
    cout << mVector[i];

vector<int>::iterator it;
for (it = mVector.begin(); it != mVector.end(); it++)
    cout << *it;

copy(mVector.begin(), mVector.end(), ostream_iterator<int>(cout, " "));

Another Example

Reverse a vector

reverse(mVector.begin(), mVector.end());

Reverse a string

reverse(mString.begin(), mVector.end());

STL Vector

Provides array-like container:

• Contiguous block of memory.
• Random access is O(1).
• Insertion O(1) at the end but O(n) elsewhere.
• Automatic and dynamic memory management.
• Modifying container will invalidate iterators.

STL Deque

Like vector but supports O(1) insertion and deletion at the beginning of container:

• Elements are stored in pages or chunks.
• Can be slower than vector, but not by much.

mDeque.push_back(1);
mDeque.push_front(2);   // Not supported by vector
mDeque.pop_front();     // Not supported by vector
mDeque.pop_back();

Complete deque example.

Summary

• STL provides lots of common data structures and algorithms.
• Iterators used throughout STL.
• Vectors and Deques provide array-like containers with O(1) random access and dynamic automatic memory management.