GCSE Computer Science: Algorithms

GCSE Computer Science: Algorithms

1. Representing Algs

   • Pseudocode
   • Flowcharts
   • Inputs Processes Outputs
   • Sequence Selection Iteration

2. Efficiency

   • One problem -> many algorithms
     • eg Bubble Merge Quick sorts
   • Time
     • Different algs give same result
       • Fast or slow?

3. Searching Algs

   • Linear
   • Binary

4. Sorting Algs

   • Bubble
   • Merge
     • MergeSort (Array(First..Last)) Begin If Array contains only one element Then Return Array Else Middle= ((Last + First)/2) rounded down to the nearest integer LeftHalfArray = MergeSort(Array(First..Middle)) RightHalfArray = MergeSort(Array(Middle+1..Last)) ResultArray = Merge(LeftHalfArray, RightHalfArray) Return ResultArray EndIf End MergeSort

5. Definitions

   • Decomposition
     • breaking a problem into a number of sub-problems, so that each  sub-  problem accomplishes an identifiable task
   • Abstraction
     • the process of removing unnecessary detail from a problem
   • Algorithm
     • A sequence of instructions to complete a task in a finite amount of time