STL Stuff

// Iterators - Entity with which you can access data within a container with certain restrictions.


 STRING

 1) append() - inserts additonal character at the end of the string. Can also use '+' or '+=' operator.
 2) begin() - Returns an iterator pointing to the first character. Runs in O(1) time.
 3) clear() - Erases all the contents of the string and puts "" of length zero. Time is O(1).
 4) compare() - Compares values of two strings. Runs in O(N+M) n beings size1 and m being size2.
 5) copy() - Copies the substring of the string in the string passed as parameter and returns the number of characters copied.
 6) empty() - Returns a bool value. true if string is empty and false otherwise. Runs in O(1) time.
 7) erase() - Deletes a substring of the string.
 8) find() - Serches the string and returns the first occurance of the parameter in the string.
 9) length() - Returns the length of the string. Time complexity is O(1).
 10) size() - Returns the length of the string. Time complexity is O(1).
 11) substr() - Returns a string which is the copy of the substring. Runs in O(N) where n is size of the substring.
   
   
VECTOR   

  1) at() - Returns the reference to the element at a particular position. Time complexity is O(1).
  2) back() - Returns reference to the last element. Time complexity is O(1)
  3) begin() - Returns an iterator pointing to the first element of the vector. Time complexity is O(1).
  4) clear() - Delets all the elments of the vector and assign an empty vector to it. Time complexity is O(N)
  5) empty() - Returns a bool value. true if vector is empty and false otherwise. Time complexity is O(1)
  6) end() - Returns an iterator pointing to a position which is next to the last element of the vector. Time complexity is O(1)
  7) erase() - Delets a single element of a single element. 
  8) front() - Returns an iterator pointing to the first element. Time complexity is O(1)
  9) insert() - Inserts a new element into a new vector 
 10) pop_back() - Removes the last element of the vector. Time complexity is O(1)
 11) push_back() - Inserts a new element at the end of the vector. Time complexity is O(1)
 12) resize() - Resizes the vector to the new length which can be less/greater than the current length.Time complexity is O(N)
 13) size() - Returns the number of elemnts in the vector. Time complexity is O(1)
  
   
 SET and MULTISET
 
  1) begin() - Returns an iterator pointing to the first element of the set. Time complexity is O(1).
  2) clear() - clears all the elements.
  3) count() - Returns 1 is element is in the set else 0
  4) empty() - Returns 1 if set is empty else 0
  5) end() - Returns an iterator pointing to the position which is next to the last element.
  6) erase() - Delete a particular element or range of elements from the set.
  7) find() - Returns iterator to the value if found else returns end() iterator. Time complexity is O(logN)
  8) insert() - Insert a new element. Time complexity is O(logN)
  9) size() - Returns the size
  
  MAP
  
  
  1) at() - Returns the mapped value of the element identifies by the key
  2) count() - 1 if match found else 0
  3) clear() - clears the map
  4) begin() - Iterator refering to the first element of the map
  5) end() - Returns the iterator pointing to the theoretical element which follows the last element
  6) empty() - 1 if empty else 0
  7) erase() - removes a single element or a range of elements from the map
  8) find() - If present return iterator pointing to it else return end() iterator. Time complexity is O(logN)
  9) insert() - inserts a single element in O(logN) is position not given with value else time is O(1)
  
  
  UNORDERED MAPS
  
  1) find() - returns iterator to element if found else the end() iterator
  2) rehash() - sets the number of buckets in the container to n
  3) insert() - inserts a new key value pair into the container
  4) erase() - Removes either a single element or a range of elements
  5) count() - 1 if key exists else 0
  6) load_factor() - Returns a floating value denoting the current load factor in the container. load_factor = current_size/bucket_count
  7) clear() - clears the map
  8) begin() - Iterator refering to the first element of the map
  9) end() -  Returns the iterator pointing to the theoretical element which follows the last element
  10) operator() - if k matches the key of the element in the container , the function returns a reference to its mapped value