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Tech Talk 3

Bubble Sort

• Compares two numbers at a time.
• Goes down the list comparing numbers.
• After one iteration, the biggest number is sent to the end of the list
• List starts ordering it self from the right
• Big O notation: O(n^2)

Insetion Sort

• Insertion sort is a simple sorting algorithm that works similar to the way you sort playing cards in your hands.
• The array is virtually split into a sorted and an unsorted part.
• Values from the unsorted part are picked and placed at the correct position in the sorted part.
• Big O notation: O(n^2)

Selection Sort

• The selection sort algorithm sorts an array by repeatedly finding the minimum element from unsorted part and putting it at the beginning.
• Uses two sub arrays
• Minimum element is moved to the begining of sub array
• Big O notation: O(n)

Merge Sort

• It divides the input array into two halves, calls itself for the two halves, and then merges the two sorted halves.
• Uses Recursive methods to merge split arrays
• Big O Notation: O(nlogn)

Tech Talk 2

Math Symbols:

• PEMDAS, each operator has its own precedence (priority)
• Add exponent ^ operator with priority 3
• Helper definition for supported operators

  private final Map<String, Integer> OPERATORS = new HashMap<>();
  {
  // Map<"token", precedence> 
  OPERATORS.put("*", 3);
  OPERATORS.put("/", 3);
  OPERATORS.put("%", 3);
  OPERATORS.put("+", 4);
  OPERATORS.put("-", 4);
  }

Math Original Expression (String):

2 + 2
4 * 6 + 3
5 + 1 * 8
(7 + 5) * 9
Tokenization (Array):

[2, +, 2]
[4, *, 6, +, 3]
[5, +, 1, *, 8]
[(, 7, +, 5, ), *, 9]
Reverse Polish Notation (Array, works well with Stack):

[2, 2, +]
[4, 6, *, 3, +]
[5, 1, 8, *, +]
[7, 5, +, 9, *]

Tech Talk 1

Generics

• We have to create duplicate code for differnet types without genrics.
• Can create objects with generics. Type has to be an object type. Ie: Integer, not int
• Can pass in as parameters. T var
• Good for code reusibility.

  Linked List

• List which has address for previous values and next values.
• Multiple peices of data is stored in a node.
• Nodes can have the adress of the previous node, the address of the node after and the data that this node contains.
• Memory does not have to be linear.
• Slower to use than a regular list.

Tech Talk 0

• A data structure is a method of organizing data.
• There are many algorithms for different purposes, and they interact with different data structures. Think of algorithms as dynamic underlying pieces that interact with data structures.
• Data Structures and Algorithms can be written using different paradigms.
• An imperative program consists of commands for the computer to perform to achieve a result. Imperative programming focuses on describing “how” a program code works.
• Object-Oriented programming (OOP) is a programming paradigm that relies on the concept of classes and objects.