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Matthew Lurie
3,512 PointsLost. "Using the value of counter as an index value..." That plus the rest of the sentence I am totally lost on.
"Using the value of counter as an index value, retrieve each value from the array and add it to the value of sum."
Don't know what I'm doing.
let numbers = [2,8,1,16,4,3,9]
var sum = 0
var counter = 0
// Enter your code below
while counter < numbers.count {
counter += 1
sum
}
4 Answers
Ben Reynolds
35,170 Pointssum = sum + numbers[counter]
That looks right (i think sum += numbers[counter] would also work). Can you share the full code for your loop so I can see it in context? Make sure you're adding to sum before you increment the counter.
Could we have written "var banana = 0"
Totally. "counter" is not a keyword, just a common name for a loop counter. Most of the time you'll probably see people just use the letter "i" which stands for index or increment depending who you ask.
Ben Reynolds
35,170 PointsWe have an array called numbers, and every item in it has an index. The first index is 0 with a value of 2, the second is 1 with a value of 8 and so on.
To grab an item from the array we use that index, so to get the first number it would be numbers[0] which would return 2
In the loop, we have a counter that also starts at 0, so you can get the first thing in the array like this:
numbers[counter]
Since counter happens to be 0 at this stage, numbers[counter] will equal 2, which can be added to "sum".
At the end of each loop iteration the counter should go up by 1, so the second time the loop runs, numbers[counter] would be the same as numbers[1] and so on until the loop condition becomes false and the loop stops.
Matthew Lurie
3,512 PointsOk tried this and it isn't working: sum = sum + numbers[counter]
I'm following what you wrote. Just not following how to get from what you wrote to "retrieve each value from the array add it to the value of sum."
Retrieve each value: numbers[counter]. That just gets me whichever value the numbers array happens to be on - so it gets me 2, 8, 1...
How do you add up each one? I guess that's what I'm confused about.
Separately, why does "counter" get us the index - is that an official word for figuring out which part of an index you're on? Could we have written "var banana = 0" and Swift would have allowed us to use that to find the index of the array?
Matthew Lurie
3,512 Pointsok got it!
The issue was that I wasn't putting it before I incremented the counter!
Which leads me to: Why does it matter if I put it before or after?
Thanks for the clarification on "counter" - it's always tricky to remember what is official keywords ("var" "print") and what is just the common parlance.
Ben Reynolds
35,170 PointsThe reason it has to go after is that incrementing the counter prepares it for the next loop iteration, not the current one. So if counter = 0, and then you bump it up to 1 right away before the sum gets updated, then this line...
sum += numbers[counter]
...would be equivalent to sum += numbers[1] during the very first pass. Index 0 would get skipped altogether.
Matthew Lurie
3,512 Pointsjust barely getting it...:) thanks for your help!