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add: slice adv. ops. exercises

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Inanc Gumus
2019-03-05 23:32:32 +03:00
parent e379976af4
commit 9c96082326
19 changed files with 810 additions and 99 deletions
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4
x-tba/slices/20-png-parser-project/main.go
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@@ -25,8 +25,10 @@ func main() {
return
}
report()
img = append([]byte(nil), img[:24]...)
img = img[:24:24]
// img = img[:24:24] // unnecessary
report()
// s.PrintBacking = true
// s.MaxPerLine = 8

68
x-tba/slices/exercises/README.md
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@@ -1,68 +0,0 @@
# Slice Exercises
---
# ANNOUNCEMENT
I teach you what the other courses don't even care to teach.
**What's new?**
* New Section: Advanced Slice Operations
* New Exercises for the Slice Internals
* New Exercises for the Slices: Advanced Operations
**What are you going to learn?**
* Full Slice Expressions: Limiting access to the backing array
* Make(): Preallocation
* Copy(): Efficiently and safely copy elements without using a loop
* Multi-Dimensional Slices
**What's coming next?**
* Empty Filer Finder: Your first taste of file operations.
* Bouncing Ball: Create a bouncing ball animation on a 2D surface.
* Png Parser: Parse a PNG file by hand and tell its dimensions.
These lectures will be added in the next 3 weeks.
**Statistics:**
* +1 hour of additional content!
* +5 new lectures
* +20 new questions
* 3 + ? new exercises
**Total content in the slices section:**
* ? hours
* ? lectures
* ? questions
* ? exercises
---
## Full Slice Exp + Make + Copy + Multi-Dim Slices
# FIX THIS
1. **[Limit the backing array sharing](https://github.com/inancgumus/learngo/tree/master/16-slices/exercises/??-limit-the-backing-array-sharing)**
* fix the excess memory allocation
* return a huge slice from a func, ask the student fix it
* full slice exp: https://play.golang.org/p/SPrLspRBXdI
* copy: https://play.golang.org/p/SPrLspRBXdI
* + put \n for the beatles exercise using copy
```go
s = append(s, 0 /* use the zero value of the element type */)
copy(s[i+1:], s[i:])
s[i] = x
```
* multi dim slices batches
```go
actions := []int{0, 1, 2, 3, 4, 5, 6, 7, 8, 9}
batchSize := 3
var batches [][]int
for batchSize < len(actions) {
actions, batches = actions[batchSize:], append(batches, actions[0:batchSize:batchSize])
}
batches = append(batches, actions)
```

14
x-tba/slices/exercises/_template/main.go
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@@ -1,14 +0,0 @@
package main
// ---------------------------------------------------------
// EXERCISE: ?
//
//
//
// EXPECTED OUTPUT
//
//
// ---------------------------------------------------------
func main() {
}

11
x-tba/slices/exercises/_template/solution/main.go
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@@ -1,11 +0,0 @@
// For more tutorials: https://blog.learngoprogramming.com
//
// Copyright © 2018 Inanc Gumus
// Learn Go Programming Course
// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
//
package main
func main() {
}

20
x-tba/slices/exercises/fix-xx-limit-the-backing-array-sharing/api/api.go
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@@ -1,20 +0,0 @@
package api
var temps = []int{5, 10, 3, 25, 45, 80, 90}
// Read returns a range of temperature readings beginning from
// the `start` until to the `stop`.
func Read(start, stop int) []int {
// ----------------------------------------
// RESTRICTIONS — ONLY ADD YOUR CODE HERE
portion := temps[start:stop]
// ----------------------------------------
return portion
}
// All returns all the temperature readings
func All() []int {
return temps
}

73
x-tba/slices/exercises/fix-xx-limit-the-backing-array-sharing/main.go
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@@ -1,73 +0,0 @@
// For more tutorials: https://blog.learngoprogramming.com
//
// Copyright © 2018 Inanc Gumus
// Learn Go Programming Course
// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
//
package main
import (
"fmt"
"github.com/inancgumus/learngo/16-slices/exercises/19-limit-the-backing-array-sharing/api"
)
// ---------------------------------------------------------
// EXERCISE: Limit the backing array sharing
//
// You've created an API that returns population counts in a country.
// To do that, you return an int slice up to some portion of it.
//
// There is a program that uses your API but it appends to the slice
// that your API returns. Doing so, overwrites your API's slice's
// backing array as well.
//
// Change your API so that it prevents the overwriting when
// the client code wants to append to the returned slice from your
// API.
//
//
// STEPS
//
// 1. Open the code inside the `api/api.go` folder
//
// 2. Fix the code there (not here — but run this code after)
//
//
// CURRENT OUTPUT
//
// The following program overwrites the elements incorrectly
// You need to change your API to prevent this behavior
// ^ ^
// | |
// API's readings: [5 10 3 1 3 80 90]
// Your readings : [5 10 3 1 3]
//
//
// EXPECTED OUTPUT
//
// Now the program cannot change the API's original backing array
// (beyond the returned capacity) (so the api now owns the control)
// ^ ^
// | |
// API's readings: [5 10 3 25 45 80 90]
// Your readings : [5 10 3 1 3]
//
// ---------------------------------------------------------
func main() {
// DO NOT TOUCH THE FOLLOWING CODE
// THIS IS THE CLIENT PROGRAM THAT USES YOUR API
// YOU CANNOT CONTROL IT! :)
// reads the first three temperatures
temps := api.Read(0, 3)
// appends two new temperature readings
temps = append(temps, []int{1, 3}...)
// prints the current temperatures
fmt.Println("API's readings:", api.All())
fmt.Println("Your readings :", temps)
}

24
x-tba/slices/exercises/fix-xx-limit-the-backing-array-sharing/solution/api/api.go
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@@ -1,24 +0,0 @@
package api
var temps = []int{5, 10, 3, 25, 45, 80, 90}
// Read returns a range of temperature readings beginning from
// the `start` until to the `stop`.
func Read(start, stop int) []int {
// Uses a full slice expression to control the length of the
// backing array (or the capacity of the returned slice).
//
// So the next append allocates a new backing array, which
// in turn doesn't overwrite the temps slice's backing array.
// ^^
// ||
// / \
// | |
portion := temps[start:stop:stop]
return portion
}
// All returns all the temperature readings
func All() []int {
return temps
}

23
x-tba/slices/exercises/fix-xx-limit-the-backing-array-sharing/solution/main.go
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@@ -1,23 +0,0 @@
// For more tutorials: https://blog.learngoprogramming.com
//
// Copyright © 2018 Inanc Gumus
// Learn Go Programming Course
// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
//
package main
import (
"fmt"
"github.com/inancgumus/learngo/16-slices/exercises/19-limit-the-backing-array-sharing/solution/api"
)
func main() {
temps := api.Read(0, 3)
temps = append(temps, []int{1, 3}...)
fmt.Println("API's readings:", api.All())
fmt.Println("Your readings :", temps)
}