Q4

CPSC 110 Spring 2012 Quiz 4 (Redo)

Instructions: The first problem asks you to read a function and determine what it does. The second problem asks you to write a function given a description.

What value would function(4, 7) return? Show your work.

# Comment: A function with 2 parameters

To function(M, N):
  Set global Var to 0
  While M <= N do:
     Set Var to Var + M
     Set M to M + 1
  Return Var

Interations M    N     Var    M <= N  Var + M
----------------------------------------------
Initiallly  4    7      0     True     0 + 4 = 4
1           5    7      4     True     4 + 5 = 9
2           6    7      9     True     9 + 6 = 15
3           7    7      15    True     15 + 7 = 22
4           8    7      22    False    The answer is 22

Define a function named sumOdds(aList) that will compute the sum of the odd numbers in aList. For example, if we call the function with the list [1,2,3,4,5] as in
```
    sumOdds( [1,2,3,4,5] )
```
it will return 9 because 1 + 3 + 5 = 9.
```
To sumOdds( aList ) :
   Set global Sum to 0
   For each Num in aList do:
      If remainder(Num, 2) = 1 then do:    // I.e. If Num/2 gives a remainder of 1
         Set global Sum to Sum + Num
   Return Sum
```
Instructions: The next two problems ask you to read and write loop algorithms.

Suppose you have a variable named list that contains the following values: [10,20,3,4,5,20,7,8,9]. What would be the final value of Var as a result of the following algorithm?

# Comment: What is the final value of Var

   Set global Var to 0
   For each item in list do:
      If item > length(list) then do:
         Set Var to Var + item

Interations Var  Item  length(list) item > length(list)  List = [10, 20, 3, 4, 5, 20, 7, 8, 9]
----------------------------------------------------------------------------------------------
Initiallly  0    10     9            True, so add 0 + 10
1           10   20     9            True, so add 10 + 20
2           30   3      9            False
3           30   4      9            False
4           30   5      9            False
5           30   20     9            True, so add 30 + 20
6           50   7      9            False
7           50   8      9            False
8           50   9      9            False  The final value of Var is 50

Convert the loop algorithm in problem #3 (above) to an equivalent while loop. Be careful about indentation.

Set global Var to 0
Set global Index to 1
While Index <= length(list) do:
   Set Item to list item at Index
   If Item > length(list) then do:
         Set Var to Var + item
   Set Index to Index + 1