DATA STRUCTURES ACM EXECUTIVE BODY 2k11

 A series of elements of same type  Placed in contiguous memory locations  Can be individually referenced by adding an index to a unique identifier  Example: Sort 10^7 numbers ranging from 100 to 200. ARRAY

 Abstract Data Types (ADTs) or data structures or collections store data and allow various operations on the data to access and change it  Why Abstract? ◦ Specify the operations of the data structure and leave implementation details to later  Every collection ADT provides a way to : insert, remove, find and access a data item Abstract Data Type (ADT)

 Last In First Out (LIFO)  Operations ◦ Push ◦ Pop ◦ Top ◦ isEmpty (Underflow) ◦ isFull (Overflow) STACK Data 4 Data 3 Data 2 Data 1

 Infix to Postfix Conversion  Matching tags in XML/HTML  Undo sequence in a text editor  Implementing functional calls (Recursion)  History of Web Browsers Applications of Stack

 Balancing Of Parenthesis ◦ Given a sequence of ‘(‘ and ‘)’ ◦ Validate the sequence ◦ A sequence is valid if for every ‘(‘, there is a counter-balancing ‘)’ which occurs only later in the sequence ◦ Examples  (()()()) : Valid  (()(() : Invalid  )()()( : Invalid Problems

 Nearest Smaller Element ◦ Given a sequence of integers ◦ For every integer, output the nearest integers to the left and to the right which are smaller to it. ◦ If there is no such number, output -1. ◦ Example  (-1,1) (-1,-1) (1,4) (1,-1) (4,-1) Problems

 Maximum Rectangle Area in a Histogram  Maximum Rectangular Area = 4x6 = 24 Problems

 Water Harvesting ◦ Find the maximum volume of water that can be collected in between the adjacent buildings ◦ Maximum Volume Of Water Collected = = 9 Problems

 First In First Out (FIFO)  Operations ◦ Enqueue (Insert) ◦ Dequeue (Remove) ◦ Front ◦ Rear / Back ◦ isEmpty ◦ isFull Queue Data 1Data 2Data 3Data 4

 Operating System Job Scheduling  Breadth First Traversal of a Graph  Level Order Traversal of a Binary Tree Applications

 Print first 100 numbers comprising only of 1s, 3s and 5s.  The first few numbers in the sequence are  1,3,5,  11,13,15,31,33,35,51,53,55,  111,113,115,131,133,135,151,153,155,311, and so on. Problem

9/14/2015 Circular Queue  Complete use of space  Uses single, fixed size buffer, as if it were connected from end to beginning

 An generalized queue, for which elements can be added to or removed from either the front or the rear.  Operations: ◦ PushBack ◦ PushFront ◦ PopBack ◦ PopFront ◦ Front ◦ Back Deque

 Given an array and an integer k, find the maximum element for each and every sub- array of size k  Example: ◦ a = [ 8, 5, 10, 7, 9, 4, 15, 12, 19, 13 ] ◦ k = 4 ◦ Output : [ 10, 10, 10, 15, 15, 19, 19 ] Problems on Deque

 Input Restricted Deque ◦ Deletion can be made from both ends ◦ Insertion can be made at one end only  Output Restricted Deque ◦ Insertion can be made at both ends ◦ Deletion can be made at one end only Variations of Deque

 Standard Template Library  Part of ISO standard C++ library  Why Use STL ◦ Reduces Development time ◦ Highly Reliable Code ( no or small amount of debugging effort required ) ◦ Highly Robust ( Container size grows automatically ) ◦ Portable and easily maintainable STL

 Templates allow the usage of generic types ◦ Advantage: no need of writing the same code all over again for a different data type  Example: ◦ template // X can represent any data type that support the operations class ABC { ABC() { } public: getMax(X a, X b) { return (a > b ? a: b); } }; ABC a; max_val = a.getMax(15.30, 53.12); Templates

 Including the library ◦ #include  Declaration ◦ stack s;  Push Operation ◦ s.push(5);  Pop Operation ◦ s.pop();  Access the Top Element ◦ int x = s.top();  Check if Stack is Empty ◦ if ( s.empty() ) cout<< “ Stack is Empty ” << endl; STL - Stack

 Including the library ◦ #include  Declaration ◦ queue q;  Push Operation ◦ q.push(5);  Pop Operation ◦ q.pop();  Access the Top Element ◦ int x = q.front();  Check if Stack is Empty ◦ if ( q.empty() ) cout<< “ Queue is Empty ” << endl; STL - Queue

 Including the library ◦ #include  Declaration ◦ deque dq;  Push Operation ◦ dq.push_back(5); ◦ dq.push_front(5);  Pop Operation ◦ dq.pop_back(); ◦ dq.pop_front();  Access the front and back elements ◦ int x = dq.front(); int y = dq.back();  Check if Stack is Empty ◦ if ( dq.empty() ) cout<< “ Deque is Empty ” << endl; STL - Deque

9/14/2015 STL-Map Introduction  Associative data structure ◦ a value is associated with the key  Stores the values in an order, sorted by the key values.  Internally implemented as a balanced BST  Multimap is used if multiple associated entries are allowed for same key values.

9/14/2015 STL- Map  Including the library ◦ #include  Declaring a map ◦ map m;  Inserting a value ◦ m.insert( pair ("abc", 2); ◦ m["abc"]=2;  Finding a value ◦ if( m.find("abc") != m.end() ) cout << "Not found" << endl;  Clear all entries ◦ m.clear();

9/14/2015 STL- Pair and Vector  Vector ◦ Dynamic array of variables, struct or objects of same type ◦ Resizes itself when inserting or erasing an element  Pair ◦ A simple associative container consisting of a 2- tuple of data elements or objects, denoted by ‘first' and ‘second'

9/14/2015 STL- Vector  Including the library ◦ #include  Declaration ◦ vector v; //1-D ◦ vector v[10000] ; //2-D  Pushing a value ◦ v.push_back(5); //1-D ◦ v[i].push_back(5); //2-D  Removing a value ◦ v.pop_back(); //1-D  Accessing an element at position i ◦ int x= v[i]; //1-D  Clear all entries ◦ v.clear(); //1-D

9/14/2015 STL- Pair  Including the library ◦ #include  Declaration ◦ pair p;  Definition ◦ p = make_pair("abc",10);  Accessing the elements ◦ p.first ◦ p.second

9/14/2015 STL-Set  Used to store unique elements in a sorted order  Elements in a set can't be modified once they has been inserted. But they can be inserted or removed from the container.  Internally implemented as balanced BST  Multiset can be used to allow duplicate entries

9/14/2015 STL-Set  Library to be included ◦ #include  Declaration ◦ set s;  Inserting an element ◦ s.insert(5);  Removing an element ◦ s.erase(5);  Get the size of the set ◦ int x= s.size();

9/14/2015 Useful functions  int a[]={1,2,2,3,5};  vector v ( a, a+5 ) ; ◦ sort ( a, a+5 );// sort an array ◦ sort ( v.begin(), v.end() );// sort a vector ◦ next_permutation( a, a+5 );  find next permutation of elements of array ◦ prev_permutation( a, a+5 ); ◦ lower_bound( v.begin(), v.end(), 2);  find the first occurence of a value in a sorted container ◦ upper_bound( v.begin(), v.end(), 2 );

9/14/2015 Using Iterators  Used with map, vector and set  Iterator:  vector ::iterator it;//declaration  it = v.begin();// points to start of the container  it = v.end(); //points to end of the container ◦ Other operations:  it++ ;  it-- ;  it != m.end() ;  Reverse Iterator:  iterates in a reverse fashion from end to beginning  vector ::reverse_iterator it;  it = v.rbegin();  it = v.rend();

If you have any problem solving a question or understanding some concept, feel free to bug us, we will be happy to debug you… ACM Executive body o Nimesh Ghelani: o Prem Kamal: o Utkarsh Raj: o Rishikesh Jha: o Vivek Verma: o Nischal Kumar: o Chandan Agarwal: o Sanket Singhal: o Aparajita Choudhary: o Bhavini Mishra: Happy Coding… 9/14/2015