# Introduction to Data Structures and Algorithms.

### What is a data structure?
A data structure is a way of organizing data so that they can be 
accessed efficiently in the computer.
#### Types of data structures
There are two categories of data structures: **Linear** and
 **Non-linear** data structures.
**Linear data structures**

Here, elements are arranged sequentially and each element is connected to the previous and the next adjacent. Examples:

##### 1.  Arrays
Elements of the same type are stored where each element is accessed using an index

**Strength:** Access is done in constant time.

**Weakness:** Fixed size

##### 2.  Stack
 LIFO-  Last In First Out

**Strength:** Insertion and deletion are done in constant time
**Weakness:** Search is done in linear time

##### 3.  Queue
FIFO- First In First Out

**Strength:** Insertion and deletion are done in constant time

**Weakness:** Search is done in linear time

##### 4.  Linked List
This consists of nodes where each node has a data field and a reference to the next node in the list.

**Strength:** Insertion and deletion are done in constant time and has Dynamic size

**Weakness:** Requires additional memory for pointer and search is done in linear time


** Non-linear data structures**

Elements are not connected in any sequence. An element can be connected to one or more elements. Examples:
##### 1.  Trees
Elements are arranged in multiple levels. Data is stored in a node and the data is of any type.
Examples: B-Tree, Binary tree, B+ tree, Binary search tree
##### 2.  Graphs
Consists of nodes and edges. The edges connect a pair of nodes


### What is an algorithm?
An algorithm is a defined set of steps or instructions to 
be followed to solve a problem.
Algorithms can be written as flowcharts, natural languages or pseudo code.
##### Types of algorithms
- Search engine algorithm
- Greedy algorithm
- Recursive algorithm
- Backtracking algorithm
- Divide and conquer algorithm
- Sorting algorithm
#### Characteristics of algorithms

- Have well defined inputs
- Are clear and unambiguous
- Have well defined outputs
- They should be language independent

#### Importance of data structures and algorithms
- Data structures help us to organize and store data while algorithms enable us to process the data in
a meaningful way. As a programmer understanding data structures and algorithms, you will be able to write code that is efficient and reliable.