Data structures

Lecture No.01
Data Structures
Rubya Afrin
Lecturer
Northern University of Business and Technology

Data Structures
 Prepares the students for (and is a prerequisite for) the more
advanced material students will encounter in later courses.
 Cover well-known data structures such as dynamic arrays, linked
lists, stacks, queues, tree and graphs.
 Implement data structures in C++

Grading
 Attendance 5
 Class test, Assignment, Presentation 25
 Mid Term 30
 Final Exam 30
Total 100

Data Structure
 A data structure is a particular way of organizing
data in a computer so that it can be used
efficiently.
4

Need for Data Structures
 Data structures organize data ⇒ more efficient programs.
 More powerful computers ⇒ more complex applications.
 More complex applications demand more calculations.

Examples
 Array
 Linked List
 Stack
 Queue
 Tree
 Graph
 Hash
6

Array
 In computer science, an array data structure, or
simply an array, is a data structure consisting of a
collection of elements (values or variables), each
identified by at least one array index or key.
 The simplest type of data structure is a linear
array, also called one-dimensional array.
7

Arrays
 Array declaration: int x[6];
 An array is collection of cells of the same type.
 The collection has the name ‘x’.
 The cells are numbered with consecutive
integers.
 To access a cell, use the array name and an
index:
x[0], x[1], x[2], x[3], x[4], x[5]

Arrays
 Elementary data structure that exists as built-in
in most programming languages.
int main()
{
int x[6];
int j;
for(i=0; i< 6; i++)
x[j] = 2*i;
}

Array Layout
x[1]
x[2]
x[3]
x[4]
x[5]
x[0]
Array cells are
contiguous in
computer memory
The memory can be
thought of as an
array

What is Array Name?
 ‘x’ is an array name but there is no variable x. ‘x’ is not an value.
 For example, if we have the code
int a, b;
then we can write
b = 2;
a = b;
a = 5;
But we cannot write
2 = a;

Array Name
 ‘x’ is not an value
int x[6];
int n;
x[0] = 5;
x[1] = 2;
x = 3; // not allowed
x = a + b; // not allowed
x = &n; // not allowed

The LIST Data Structure
 The List is among the most generic of data
structures.
 Real life:
a. shopping list,
b. groceries list,
c. list of people to invite to dinner
d. List of presents to get

Lists
 A list is collection of items that are all of the
same type (grocery items, integers, names)
 The items, or elements of the list, are stored in
some particular order
 It is possible to insert new elements into various
positions in the list and remove any element of
the list

Lists
 List is a set of elements in a linear order.
For example, data values a1, a2, a3, a4 can be
arranged in a list:
(a3, a1, a2, a4)
In this list, a3, is the first element, a1 is the
second element, and so on
 The order is important here; this is not just a
random collection of elements, it is an ordered
collection

List Operations
Useful operations
 createList(): create a new list (presumably empty)
 copy(): set one list to be a copy of another
 clear(); clear a list (remove all elments)
 insert(X, ?): Insert element X at a particular position
in the list
 remove(?): Remove element at some position in
the list
 get(?): Get element at a given position
 update(X, ?): replace the element at a given position
with X
 find(X): determine if the element X is in the list
 length(): return the length of the list.

List Operations
 If we use the “current” marker, the following
four methods would be useful:
 start(): moves to “current” pointer to the very first
element.
 tail(): moves to “current” pointer to the very last
element.
 next(): move the current position forward one
element
 back(): move the current position backward one
element

Data structures

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