Difference between revisions of "W1351 Swap Function"
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== Prerequisites == | == Prerequisites == | ||
* [[W1301 Arrays]] | |||
== Introduction == | |||
A very common need in many algorithms is swapping the values in two variables. It's also very common that these two variables are contained within an array. | |||
== Swapping == | |||
The first approach that most students take when swapping is this: | |||
<syntaxhighlight lang="swift"> | |||
let x = 5 | |||
let y = 7 | |||
x = y | |||
y = x | |||
</syntaxhighlight> | |||
Take the time to think through what you believe will occur as the above code is executed. Then, try it. | |||
{{Observe|Section 1| | |||
# What syntax errors do you observe in the above code? | |||
# What logic errors do you observe in the above code? | |||
}} | |||
The primary issue that most students encounter in this scenario is '''overwriting''' the value of one of the variables, and then assigning this overwritten value to the other value. | |||
{{Observe|Section 2| | |||
Assuming that the syntax errors in the above code segment are resolved: | |||
# What will be the value of '''x''' after the code executes? | |||
# What will be the value of '''y''' after the code executes? | |||
}} | |||
View the following video: [https://www.youtube.com/watch?v=vzCUWAxq6lU Swapping Algorithm] (YouTube) | |||
{{Observe|Section 3| | |||
# What must be done to properly swap the values of two variables? | |||
}} | |||
== Exercises == | |||
Revision as of 19:21, 29 March 2020
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— Merlin, The Coder
Prerequisites[edit]
Introduction[edit]
A very common need in many algorithms is swapping the values in two variables. It's also very common that these two variables are contained within an array.
Swapping[edit]
The first approach that most students take when swapping is this:
let x = 5
let y = 7
x = y
y = x
Take the time to think through what you believe will occur as the above code is executed. Then, try it.
Observe
Observe, Ponder, and Journal: Section 1
- What syntax errors do you observe in the above code?
- What logic errors do you observe in the above code?
The primary issue that most students encounter in this scenario is overwriting the value of one of the variables, and then assigning this overwritten value to the other value.
Observe
Observe, Ponder, and Journal: Section 2
Assuming that the syntax errors in the above code segment are resolved:
- What will be the value of x after the code executes?
- What will be the value of y after the code executes?
View the following video: Swapping Algorithm (YouTube)
Observe
Observe, Ponder, and Journal: Section 3
- What must be done to properly swap the values of two variables?
