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Questions and Answers
What type of value does the second parameter in typical STL algorithms usually represent?
Which of the following STL algorithms is responsible for applying a function to each element within a specified range?
What does the find_if() algorithm return?
Which algorithm is used to change the order of elements randomly?
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What is the purpose of the transform() algorithm in STL?
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What type of class templates does STL provide for function objects?
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Which of the following statements is true regarding the sort() algorithm?
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What is a common use of the STL function object class template 'plus'?
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What is the main principle behind STL algorithms?
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Which type of STL algorithms does NOT change the data elements?
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Which suffix is used for predicate names that require a test function returning true or false?
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What is a characteristic of mutating STL algorithms?
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What is the role of templates in STL algorithms?
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Which algorithm is an example of a numeric STL algorithm?
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What is the benefit of using STL algorithms in software development?
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Which STL algorithm category specifically deals with sorted ranges?
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What is the primary purpose of the back_inserter() function in STL?
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What design pattern do STL adaptors implement?
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Which of the following is NOT a function of STL functor adaptors?
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How does a binder work in the context of STL function adaptors?
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Which of the following is NOT a type of container adaptor?
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Which statement accurately describes the role of a negator in STL?
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How does a stack container adaptor handle elements?
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What is the function of mem_fn in STL?
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What type of access does a queue container adaptor provide?
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Which iterator adaptor allows iterating backward through a container?
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Which of the following statements about binders is true?
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In a priority_queue adaptor, how is the highest priority item managed?
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What does the not_fn() function achieve in the context of negators?
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What do bind1st() and bind2nd() functions specifically do?
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What can STL iterator adaptors be used for in conjunction with algorithms?
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Which statement is true regarding STL container adaptors?
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Study Notes
STL Algorithm Overview
- STL Algorithms operate over iterators, not containers.
- Each container declares an iterator and a const iterator as a trait.
- Vectors and Deques have random access iterators.
- Lists, maps, sets, multimaps, and multisets have bidirectional iterators.
- Containers declare factory methods for its iterator type: begin(), end(), rbegin(), rend().
- Composition of algorithms with a container is done by invoking the algorithm with iterators for that container.
- Templates provide compile-time type safety for combinations of containers, iterators, and algorithms.
Algorithm Categories
- Non-mutating algorithms operate using a range of iterators, but do not change the data elements found.
- Examples: count(), equal(), find(), search()
- Mutating algorithms operate using a range of iterators and can change the order of the data elements.
- Examples: copy(), remove(), fill(), replace(), rotate()
- Sorting and Sets algorithms sort or search ranges of elements and act on sorted ranges by testing values.
- Examples: sort(), nth_element(), binary_search()
- Numeric algorithms produce (generally) numeric results
- Examples: min(), min_element(), next_permutation()
Benefits of STL Algorithms
- STL algorithms are decoupled from the particular containers they operate on and are parameterized by iterators.
- All containers with the same iterator type can use the same algorithms.
- Algorithms are written to work on iterators, reducing software development effort.
Specific Algorithm Suffixes
- Predicate names ending in the "_if" suffix require a predicate test function as an argument.
- Predicate names ending in the "_n" suffix iterate a fixed number of times instead of over a range.
for_each()
- Applies the function object f to each element in the range from first to last.
- f's return value is ignored.
Search and Sorting Algorithms
-
find(first, last, value)
- Returns a forward iterator at the first element in the sequence range that matches the provided value.
-
find_if(first, last, pred)
- Returns a forward iterator at the first element in the sequence range for which the predicate is true.
-
sort()
- Sorts the elements
-
binary_search()
- searches sorted ranges in the container.
Mutating Algorithms
-
copy(), copy_backward()
- Copy the elements of a range to a new container.
-
swap(), swap_ranges()
- Swap elements of a range with elements of another range.
-
replace(), replace_if(), replace_copy(), replace_copy_if()
- Replace elements in a range with a new value.
-
fill(), fill_n()
- Set the values of a range to a specified value.
-
remove(), remove_if()
- Remove elements in a range that match a specified condition.
-
random_shuffle()
- Shuffle the elements in the given range by using the Fisher-Yates algorithm.
transform()
- Scans a range and for each element applies a function to generate a new object, which is stored in a second container (or takes two intervals and applies a binary operator to items to generate a new container).
Function Objects
- Also known as functors, declare and define the operator().
- STL provides helper base class templates unary_function and binary_function.
- STL provides common-use function object class templates:
- Arithmetic: plus, minus, times, divides, modulus, negate
- Comparison: equal to, not equal to, greater, less, greater equal, less equal
- Logical: logical and, logical or, logical not
- A number of STL generic algorithms can take STL-provided or user-defined function object arguments to extend algorithm behavior.
STL Adaptors
- Implement the Adaptor design pattern, converting one interface into another.
- Container adaptors: stack, queue, priority_queue
- Iterator adaptors: reverse_iterators() and back_inserter()
- Function adaptors: negators and binders
- STL adaptors can be used to narrow interfaces (e.g., a stack adaptor for vector).
Container Adaptors
- Near-containers, similar in concept to first-class containers, but without all capabilities.
- Do not provide the actual data structure implementation.
- Do not support iterators.
Stack Container Adaptor
- Adapts a vector, list, or deque, defining a LIFO data structure.
- Permits the use of push() and pop().
Queue Container Adaptor
- Inserts data at the back of the underlying data structure and deletes from the front, defining a FIFO data structure.
Priority Queue Container Adaptor
- Provides insertions in sorted order into the data structure and deletions from the front.
- Implemented using the vector class by default.
- Insertions occur such that the highest priority item is inserted at the front of the queue.
Iterator Adaptors
- Used in STL algorithms that copy elements (e.g., copy(), unique-copy(), copy_backwards(), remove_copy(), replace_copy()).
- With each element copied, the value is assigned and the iterator is incremented.
- Require the target container to have sufficient size to hold the assigned elements.
- Can be used to expand containers as the algorithm executes (e.g., using inserter with algorithms to grow the container).
back_inserter()
- Causes the container’s push_back() operator to be invoked instead of the assignment operator.
- The argument passed is the container itself.
Function Adaptors
- Pre-defined functors that change their function to:
- Perform function composition and binding
- Allow fewer created functors
- Permit combining, transforming, and manipulating functors with:
- Each other
- Certain values
- Special functions
- Binders (bind, bind1st, and bind2nd)**: Bind arguments to functors.
- Negators (not_fn, not1, and not2)**: Adapt functors by negating arguments.
- MemberFun (mem_fn, mem_fun, mem_fun_ref)**: Convert a member function into a callable functor.
Binder
- Transforms an n-ary functor into a lesser functor by acting as a converter between the functor and an algorithm.
- Always stores both the binary functor and the argument internally.
- Arguments are passed to the functor every time it is called.
Negator
- Stores the opposite result of a functor.
- not_fn(obj) negates the result of a callable object.
- not1(op)* negates the result of a unary op.
- not2(op)* negates the result of a binary op.
mem_fn
- Allows class member functions or C-style functions as arguments to STL pre-defined algorithms.
- mem_fn(PtrToMember mf) converts a pointer to member to a functor whose first argument is an instance of the class.
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Description
Explore the various categories of STL algorithms in C++. This quiz covers the operation of non-mutating and mutating algorithms, as well as how these algorithms interact with different types of iterators and containers. Test your understanding of key concepts and examples in this essential area of C++ programming.
