Swift control flow

Question

Task: 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.

I just cannot figure out what I am doing wrong.

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]
counter += 1
}

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

Answer 1 · 2017-12-16T08:14:20Z

December 16, 2017 8:14am

The numbers.count returns the actual number of entities within the array and therefore starts at "1" and returns "7". The array begins with "0" ends at "6". Thus when iterating through the array, when the counter reaches "6" (the last entity in the array), the number count is still "7", causing the loop to run an extra cycle and look for the numbers[7] array entity which doesn't exist.

The simple solution would be to offset the numbers.count to match the array numbering by subtracting 1 from numbers.count.

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

Welcome to the Treehouse Community

Looking to learn something new?

Linden Hausmann

Linden Hausmann

Swift control flow

1 Answer

Kevin Tan

Kevin Tan

Jennifer Nordell

Jennifer Nordell