Algorithms

• Counting is one of the simplest algorithms to understand

  • Algorithm to count from 1 to 10
  • FOR i ← 1 TO 10
  • OUTPUT i
  • Output: 1 2 3 4 5 6 7 8 9 10
  • Algorithm to count in twos (even numbers only)
  • FOR i ← 2 TO 10 STEP 2
  • OUTPUT i
  • Output: 2 4 6 8 10
  • When we count, we need a variable to store the counter in. This is called the iterator
• Average algorithm

  For a sushi conveyor, how could you find the average price of the items on the conveyor?

  Total ← 0

  Count ← 0

  WHILE SushiDetected

  Count ← Count + 1

  Total ← Total + Price

  ENDWHILE

  Average ← Total/Count
• Totalling algorithm

  For a sushi conveyor, how could we find the total cost of all sushi on the conveyor?

  Total ← 0

  WHILE SushiDetected

  Total ← Total + Price

  ENDWHILE
• Lowest algorithm

  For a sushi conveyor, how could we find the cheapest item on the conveyer?

  CheapestItem ← 0

  FirstItem ← TRUE

  WHILE SushiDetected

  IF FirstItem

  THEN

  CheapestItem ← FirstItem

  ELSE

  FirstItem ← FALSE

  IF PRICE < MIN

  MIN ← PRICE

  ENDIF

  ENDIF

  ENDWHILE
• In a linear search, the items are examined in the sequence of the list.
• Sorting

  Data sets often need to be sorted.

  Data sets can be sorted by:

  • Count Order
  • Alphabetical Order
  • Reverse alphabetical or count order
• Bubble Sort

  1. Start with the left-most item
  2. Compare it to the one next to it
  3. If the one next to it is less, swap the items
  4. Repeat for all other items
  5. At the end of one pass through the list, the largest item is at the end of the list.

  Repeat the process until all the items are sorted

  Each pass results in the next last item being sorted