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iOS Swift Collections and Control Flow Control Flow With Loops Working With Loops

Maxwell Catmur
Maxwell Catmur
7,355 Points
Posted by Maxwell Catmur
Maxwell Catmur
7,355 Points

How do you add integers of arrays together?

Here is the question:

Now that we have the while loop set up, it's time to compute the sum! Using the value of counter as an index value, retrieve each value from the array and add it to the value of sum.

For example: sum = sum + newValue. Or you could use the compound addition operator sum += newValue where newValue is the value retrieved from the array.

Here is the code I have typed. Please can you let me know what I've done wrong?

let numbers = [2,8,1,16,4,3,9] var sum = 0 var counter = 0

while counter < numbers.count { sum += numbers[] counter += 1 }

Thanks

loops.swift 
let numbers = [2,8,1,16,4,3,9]
var sum = 0
var counter = 0

// Enter your code below

while counter < numbers.count {
    sum += numbers[]
    counter += 1
}

2 Answers

Michael Hulet
Michael Hulet
47,913 Points
Michael Hulet
Michael Hulet
47,913 Points

You can't just add all the elements of an array together like that, though it'd be cool. Using a for loop instead of a while loop with a counter would be right up this question's alley

Maxwell Catmur
Maxwell Catmur
7,355 Points
Maxwell Catmur
Maxwell Catmur
7,355 Points

Thank you. But this question is specifically requesting for me to use a while loop.

Michael Hulet
Michael Hulet
47,913 Points
Michael Hulet
Michael Hulet
47,913 Points

Ohh lol that's what I get for just answering without looking at the question :P In that case, your code looks mostly good, but to get a value out of an array, you need to provide a number to its subscript. For example numbers[0] gets the first value in the numbers array. What variable in your code starts at 0 and increases by 1 for as many objects as there are in the numbers array?

Maxwell Catmur
Maxwell Catmur
7,355 Points
Maxwell Catmur
Maxwell Catmur
7,355 Points

Thank you very much Michael; it works! :D

mrtroy
mrtroy
8,069 Points
mrtroy
mrtroy
8,069 Points

It looks like you forgot to use the index value for numbers inside the while loop. As you go through the loop counter will start as zero and end up with the number or items in "numbers[]" minus one. In this case counter will go from zero to six.

You can test that by putting a print(counter) inside the loop. Try it just before the sum is added.

Once you have done that change the print to be "print(numbers[counter])" and you can see each element in the array. You should be able to see what to do next to fix that sum addition statement.

Happy coding!

PS. I know you got your answer a few hours ago but I still wanted to give you some troubleshooting tips. Put some print statements in a loop to see what it is doing.