Review #

This page contains information and coding exercises for all our pseudocode topics: variables, loops, arrays, parallel arrays, searching, methods, sorting,collections.

Open up the pseudocode compiler in a new tab. You will be using this website to complete the exercises below.

👾 💬
Make sure you are never using output/return inside an if statement! ❌
Instead, use a variable to store the output/return value, and output/return it at the end ✅

Conditionals, Loops, Mod #

👾 💬
Remember, you can use a mod b or a%b to find the remainder after integer division a//b.
If the remainder is 0, that means a is evenly divisible by b.

💻 Write a method that outputs a checkerboard pattern of `#` and `_`.

input: number of rows, number of columns
return: none

example output:

#_#_#
_#_#_
#_#_#
_#_#_
#_#_#

Answer ↕

method pattern(ROWS, COLUMNS)
  loop R from 1 to ROWS
    ONE_ROW = ""
    loop C from 1 to COLUMNS
      if ((R+C) mod 2) = 0 then
        ONE_ROW = ONE_ROW + "#"
      else 
        ONE_ROW = ONE_ROW + "_"
      end if
    end loop
    output ONE_ROW
  end loop
end method

pattern(5,5)

Collections, Array, Search, Mod #

A number is prime if it cannot be evenly divided by any number besides 1 and itself. For example 5 is prime, and can only be evenly divided by 5 and 1.

To check if n is prime, you can try dividing it by every number lower than n. If you are able to evenly divide it, it is not prime. If you try every number and none work, then it is prime.

💻 Write a method that determines whether or not a number is prime.

input: a number
return: true/false

Answer ↕

method isPrime(NUM)
  primeCheck = true

  loop I from 2 to NUM-1
     if NUM mod I == 0 then
       primeCheck = false
     end if
  end loop

  return primeCheck
end method

output isPrime(19)

💻 Write a method that searches through a collection. Each time it finds a prime number, it should add that prime number to a new array. It should return that array.

input: a collection of numbers
return: an array of all the primes found in the collection

Answer ↕

method primeSearch(NUMS_COLLECTION)
  PRIMES = []
  INDEX = 0
  NUMS_COLLECTION.resetNext()
  loop while NUMS_COLLECTION.hasNext()
    NUMBER = NUMS_COLLECTION.getNext()
    if isPrime(NUMBER) = true then
       PRIMES[INDEX] = NUMBER
       INDEX = INDEX + 1
    end if
  end loop
  return PRIMES 
end method

NUMS = new Collection()

NUMS.addItem(13)
NUMS.addItem(14)
NUMS.addItem(15)
NUMS.addItem(16)
NUMS.addItem(17)
NUMS.addItem(18)
NUMS.addItem(19)
NUMS.addItem(20)
NUMS.addItem(21)
NUMS.addItem(22)
NUMS.addItem(23)

output primeSearch(NUMS)

Collections, Arrays, Loops #

💻 Write a method that transfers the elements of a collection into an array, but in the opposite order. You may assume the collection has exactly 10 items in it.

input: a collection with 10 items
return: an array, which contains the same elements but in the opposite order

Answer ↕

method swapOrder(MY_COLLECTION)
  NEW_ARRAY = []
  INDEX = 9

  MY_COLLECTION.resetNext()
  loop while MY_COLLECTION.hasNext()
     ITEM = MY_COLLECTION.getNext()
     NEW_ARRAY[INDEX] = ITEM
     INDEX = INDEX - 1
  end loop
  
  return NEW_ARRAY

end method

NUMS = new Collection()

NUMS.addItem(14)
NUMS.addItem(15)
NUMS.addItem(16)
NUMS.addItem(17)
NUMS.addItem(18)
NUMS.addItem(19)
NUMS.addItem(20)
NUMS.addItem(21)
NUMS.addItem(22)
NUMS.addItem(23)

output swapOrder(NUMS)

Deliverables #

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