2.1 - Algorithms

2.1 - Algorithms

1. Pseudocode + Flow Diagrams

   • Pseudocode is a way to type out code without using code-like statements.
   • Pseudocode is NOT a real programming language.
   • There is no 'correct' way to write pseudocode.
   • Pseudocode is used to plan algorithms.
   • Terminator (in a flow diagram) is used at the start or at the end of its process. Eg 'Start.'
   • Process (in a flow diagram) is used to represent a process. Eg 'Area = Width*Height.'
   • Sub-Process (in a flow diagram) is used to represent a whole different process taht has to be run at this stage. Eg 'Save to file.'
   • INPUT/OUTPUT (in a flow diagram) is used to represent a stage in the code. Eg 'INPUT/OUTPUT.'

2. Searching Algorithms

   • There are two types of search algorithms. Eg 'Linear & Binary search.'
   • The following steps are for linear search : 1 - Start with the first item in the list. 2 - Compare the item to the target - if it matches then stop the search. 3 - Move onto the next item in the list. 4 - Repeat steps 2 to 3 until the item is found or every item has been checked. 5 - If every item has been checked and the target has not been found then it is not in the list.
   • The following steps are for binary search : 1 - Find the middle item in the sorted dataset using (n+1) / 2 (round up if necessary.) 2 - Compare the middle item to the target: a. if it matches then the item is found b. If the target is smaller/comes before the middle item then "cut off" the second half of the dataset including the middle item c. If the target is larger/comes after the middle item then "cut off" the first half of the dataset including the middle item. 3 - Repeat steps 1 and 2 on the new, smaller dataset until the target has been found or the dataset cannot be split any further.
   • Comparisons Of Binary And Linear Search :
     • Linear = Very Simple / Binary = More Complex
     • Linear = Inefficient / Binary = Very efficient
     • Linear = Simple Lists / Binary = Longer Lists
     • Linear = Data Does Not Need To Be Ordered / Binary = Can Only Have Search Order Lists

3. Sorting Algorithms

   • Three sorting algorithms: Merge sort, Bubble sort, Insertion sort
   • Bubble Sort : Bubble sort is where you have to swap only two at a time in order and once you have to go through the list once you have to start again.
   • Merge Sort : This is where you need to split the numbers into groups into smallest to largest then continue to do that until you get all of the numbers listed from smallest to largest.
   • Insertion Sort : This is nearly the same as bubble sort however, it is with words.