gaspersic/learngo
1
0
Fork 0
Code Issues Pull Requests Projects Releases Wiki Activity

refactor: slices 22th exercise

Browse Source
This commit is contained in:
Inanc Gumus
2019-08-18 14:56:37 +03:00
parent 55419e59b7
commit 2dab6c53c9
2 changed files with 87 additions and 54 deletions
Download Patch File Download Diff File Expand all files Collapse all files

71
16-slices/exercises/22-adv-ops-practice/main.go
View File

@ -7,9 +7,6 @@ import (
// ---------------------------------------------------------
// EXERCISE: Practice advanced slice operations
//
// This exercise's intention is warm you up and reinforce
// your memory for the advanced slice operations.
//
// Please follow the directions in the following code.
//
// To see the expected output, please run:
@ -24,7 +21,6 @@ func main() {
// or do it with your own Printf that matches the output
// of the prettyslice package.
//
// This allows you to see the backing array of the slices.
s.PrintBacking = true
// Shows 10 slice elements per line
@ -34,10 +30,10 @@ func main() {
// ########################################################
//
// #1: Create a string slice with a length and capacity
// of 5. Call the slice: `names` and print it.
// #1: Create a string slice: `names` with a length and
// capacity of 5, and print it.
//
//
// ...
// s.Show("1st step", names)
@ -51,82 +47,73 @@ func main() {
//
// Observe how the slice and its backing array change.
//
//
// ...
// s.Show("2nd step", names)
// ########################################################
//
// #3: Fix the append problem by reinitializing the
// names slice below (currently the previous code
// appends after 5 elements).
// #3: The previous code appends at the end of the names
// slice:
//
// Append the new elements to the head of the names
// slice instead.
// ["" "" "" "" "" "einstein", "tesla", "aristo"]
//
// Print the names slice.
// Append the new elements to the beginning of the names
// slice instead:
//
// HINT:
// ["einstein", "tesla", "aristo" "" ""]
//
// The problem is in the `make` function.
// So: Overwrite and print the names slice.
//
// ...
// s.Show("3rd step", names)
// ########################################################
//
// #4: Copy elements from an array to the `names` slice.
//
// Copy only the first two elements of the following
// #4: Copy only the first two elements of the following
// array to the last two elements of the `names` slice.
//
// Print the names slice (do not forget extending it
// after appending). You should print 5 elements.
// Print the names slice, you should see 5 elements.
// So, do not forget extending the slice.
//
// Observe how its backing array stays the same.
//
// Observe how the backing array stays the same.
//
// Array (uncomment):
// moreNames := [...]string{"plato", "khayyam", "ptolemy"}
//
// ...
//
// s.Show("4th step", names)
// ########################################################
//
// #5: Clone the `names` slice to the `clone` slice.
// #5: Only copy the last 3 elements of the `names` slice
// to a new slice: `clone`.
//
// But only clone (copy) the last 3 elements of the
// `names` slice.
//
// Then, append the first two elements of the `names`
// slice to the `clone` slice.
// Append the first two elements of the `names` to the
// `clone`.
//
// Ensure that after appending no new backing array
// allocations occur for the `clone` slice.
//
// Print the clone slice before and after the append.
//
//
// ...
// s.Show("5th step (before append)", clone)
//
// ...
// s.Show("5th step (after append)", clone)
// ########################################################
//
// #6: Slice the `clone` slice between 2nd and 4th
// elements.
// #6: Slice the `clone` slice between 2nd and 4th (inclusive)
// elements into a new slice: `sliced`.
//
// Put the sliced slice into a variable named:
// `sliced`.
// Append "hypatia" to the `sliced`.
//
// Append "hypatia" to the `sliced` slice.
//
// Ensure that new backing array allocation "happens".
// Ensure that new backing array allocation "occurs".
//
// Change the 3rd element of the `clone` slice
// to "elder".
@ -136,7 +123,7 @@ func main() {
//
// Print the `clone` and `sliced` slices.
//
//
// ...
// s.Show("6th step", clone, sliced)
}

70
16-slices/exercises/22-adv-ops-practice/solution/main.go
View File

@ -16,41 +16,74 @@ func main() {
s.MaxPerLine = 10
s.Width = 60
// ########################################################
//
// #1
// #1: Create a string slice: `names` with a length and
// capacity of 5, and print it.
//
names := make([]string, 5)
s.Show("1st step", names)
// ########################################################
//
// #2
// #2: Append the following names to the names slice:
//
// "einstein", "tesla", "aristo"
//
// Print the names slice.
//
// Observe how the slice and its backing array change.
//
names = append(names, "einstein", "tesla", "aristo")
s.Show("2nd step", names)
// ########################################################
//
// #3
// #3: The previous code appends at the end of the names
// slice:
//
// ["" "" "" "" "" "einstein", "tesla", "aristo"]
//
// Append the new elements to the beginning of the names
// slice instead:
//
// ["einstein", "tesla", "aristo" "" ""]
//
// So: Overwrite and print the names slice.
//
names = make([]string, 0, 5)
names = append(names, "einstein", "tesla", "aristo")
s.Show("3rd step", names)
// ########################################################
//
// #4
// #4: Copy only the first two elements of the following
// array to the last two elements of the `names` slice.
//
// Print the names slice, you should see 5 elements.
// So, do not forget extending the slice.
//
// Observe how its backing array stays the same.
//
moreNames := [...]string{"plato", "khayyam", "ptolemy"}
copy(names[3:5], moreNames[:2])
names = names[:cap(names)]
s.Show("4th step", names)
// ########################################################
//
// #5
// #5: Only copy the last 3 elements of the `names` slice
// to a new slice: `clone`.
//
// Append the first two elements of the `names` to the
// `clone`.
//
// Ensure that after appending no new backing array
// allocations occur for the `clone` slice.
//
// Print the clone slice before and after the append.
//
clone := make([]string, 3, 5)
copy(clone, names[len(names)-3:])
s.Show("5th step (before append)", clone)
@ -58,13 +91,26 @@ func main() {
clone = append(clone, names[:2]...)
s.Show("5th step (after append)", clone)
// ########################################################
//
// #6: Slice the `clone` slice between 2nd and 4th (inclusive)
// elements into a new slice: `sliced`.
//
// Append "hypatia" to the `sliced`.
//
// Ensure that new backing array allocation "occurs".
//
// Change the 3rd element of the `clone` slice
// to "elder".
//
// Doing so should not change any elements of
// the `sliced` slice.
//
// Print the `clone` and `sliced` slices.
//
// #6
//
sliced := clone[1:4:4]
sliced = append(sliced, "hypatia")
clone[2] = "elder"
s.Show("6th step", clone, sliced)