1. Recitation Outline Hash tables in C++ STL Examples Recursive example
unordered_set (multiset)
unordered_map (multimap)
Examples
Word puzzle using hash tables
Remove duplicate elements from a vector
Recursive example
Print out numbers

2. 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

3. 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

4. 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
Review the code
A demo of running the program

5. Remove Duplicate Elements
Remove duplicate elements from a vector
Examples/r7/remove_duplicate1.cpp
This version uses a hash table to record unique elements
To compile: make remove_duplicate1.x

6. 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
To compile: make printnumber_recursive.x