Unordered associative containers
Traversal with iterator
for (itr = umap.begin(); itr != umap.end(); itr++)
{
// itr works as a pointer to pair<string, double>
// type itr->first stores the key part and
// itr->second stroes the value part
cout << itr->first << " " << itr->second << endl;
}
Iterator is a pointer to an element in the container. So, use *iter or iter->member to access the element or member of the element.
unordered_set (HashSet)
Collection of unique keys, hashed by keys. (class template).
- Creation :
unordered_set<int> intSet; - Add :
intSet.insert(num); - Find :
intSet.find(num);If not found, the critieria isset.find(num) == set.end();
unordered_map (HashMap)
Collection of key-value pairs, hashed by keys, keys are unique. (class template).
- Creation :
unordered_map<string, int> wordFreq; - Add :
wordFreq[key] = 1; - Check key existance :
if(unmap.find(key) == unmap.end())
Vector
According to this tutorial.
- Creation :
vector<int> vec; - Add :
vec.push_back(num); - Get :
vec[ind]orvec.at(ind) - Remove :
vec.erase(ind) - size
- empty
- insert :
vec.insert(ind, val)
Container adaptors
Container adaptors provide a different interface for sequential containers.
stack
- empty : returns whether the stack is empty
- size : the same as all other sequential containers
- top : return the top element (next to be pushed)
- push
- pop
queue
- empty
- size
- push
- pop
- front : returns a reference to the first element of the queue.
- back : returns a reference to the last element of the queue.
priority_queue
The first element of the priority_queue is the greatest of all elements in the queue and elements are in non-increasing order.
make_heap
According to this tutorial, we can use
std::make_heapto create a heap.
Vector to Max heap :
- Creation :
std::make_heap(v.begin(), v.end()); - pop :
std::pop_heap(v.begin(), v.end()); - push : directly push to vector then run
std::push_heap(v.begin(), v.end());to heapify it.
