Utilizing Hash Tables in C++ STL for Unique Element Handling
Explore how to effectively employ hash tables in C++ STL for managing unique elements, including examples like word puzzles and removing duplicates from vectors. Dive into the functionalities of unordered_set and unordered_map to enhance your C++ programming skills.
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Presentation Transcript
Recitation Outline Hash tables in C++ STL unordered_set (multiset) unordered_map (multimap) Examples Word puzzle using hash tables Remove duplicate elements from a vector Recursive example Print out numbers
unordered_set #include <unordered_set> using namespace std; std::pair<iterator, bool> insert(const value_type& val); Insert an element val into hash table iterator find(const key_type& k); Search key k void erase(const_iterator position); size_type erase(const key_type& k); Delete an element begin() end() iterators
unordered_map #include <unordered_map> Using namespace std; std::pair<iterator, bool> insert(const value_type& obj); Insert an element typedef std::pair<const Key, T> value_type; void erase(const_iterator position); size_type erase(const key_type& k); Delete an element (with a given iterator or key) iterator find(const key_type& k); Search an element (with given key) begin(), end() Iterators mapped_type& operator[](const key_type& k); Return value if key k exists in map Otherwise an element with key k and default value will be inserted
Word Puzzle using hash table In this version we store word dictionary in an unordered_set See examples/r7/word_puzzle_ht.cpp, word_puzzle_ht.h, rotation.cpp What you need to do Review the code To compile: make To run: word_puzzle_ht.x (you can read the source code to see the supported commands)
Remove Duplicate Elements Remove duplicate elements from a vector Examples/r7/remove_duplicate1.cpp This version uses a hash table to record unique elements What you need to do Review the code To compile: make remove_duplicate1.x To run: remove_duplicate1.x
Recursive Function Convert the following function into recursive one void printnumber(size_t k) { for (size_t I = 0; I <= k; ++i) { cout << I << ; } } See Examples/r7/printnumber_nonrecursive.cpp And printnumber_recursive.cpp What you need to do Review the code To compile: make printnumber_recursive.x To run: printnumber_recursive.x some_integer_value
STL Algorithm std::swap Function signature template <class T> void swap (T& a, T& b) template <class T, size_t N> void swap(T (&a)[N], T (&b)[N]) Swap values of a and b Note that when a and b are pointers, we are swapping content of a and b (i.e., address stored in a and b), not values that a and b refer to See Example1.cpp Example2.cpp What you need to do Please review the code Please play with the code (compile and run)
STL Algorithms std::iter_swap() Function signature Template <class ForwardIterator1, class ForwardIterator2> void iter_swap(ForwardIterator1 a, FowardIterator2 b) This function swap the elements referred by the two iterators a and b Examples Example3.cpp What you need to do Please review the code Please play with the code (compile and run)
