update: slice exercises 21, 23, 24, 25, 26

16-slices/exercises/21-correct-the-lyric/hints.md

@@ -0,0 +1,17 @@
+# Hints
+
+You can use the following slice operations to solve the exercise:
+
++ Prepends "value" to the slice:
+  ```go
+  slice = append([]string{"value"}, slice...)
+  ```
+
++ Appends some part (N to M) of the same slice to itself:
+  ```go
+  slice = append(slice, slice[N:M]...)
+  ```
++ Copies the last part of the slice starting from M to the first part of the slice until N:
+  ```go
+  slice = append(slice[:N], slice[M:]...)
+  ```

16-slices/exercises/21-correct-the-lyric/main.go

@@ -51,18 +51,7 @@ import (
 //
 // HINTS
 //
-//   Only look at this if you get stuck.
+//   If you get stuck, check out the hints.md file.
-//
-//   You can use the following slice operations to solve the exercise.
-//
-//   + Prepends "value" to the slice:
-//     slice = append([]string{"value"}, slice...)
-//
-//   + Appends some part (N to M) of the same slice to itself:
-//     slice = append(slice, slice[N:M]...)
-//
-//   + Copies the last part of the slice starting from M to the first part of the slice until N:
-//     slice = append(slice[:N], slice[M:]...)
 //
 // ---------------------------------------------------------
 

16-slices/exercises/23-limit-the-backing-array-sharing/main.go

@@ -16,9 +16,21 @@ import (
 // ---------------------------------------------------------
 // EXERCISE: Limit the backing array sharing
 //
+//  GOAL
+//
+//    Limit the capacity of the slice that is returned
+//    from the `Read` function. Read on for more details.
+//
+//
+//  BEFORE YOU START
+//
 //    In this exercise: API means the api package. It's in the
 //    api folder. You need to change the code in the `api/api.go`
-//  to solve this exercise.
+//    to solve this exercise, and you need import the api
+//    package.
+//
+//
+//  WHAT IS THE PROBLEM?
 //
 //    `Read` function of the api package returns a portion of
 //    its `temps` slice. Below, `main()` saves it to the
@@ -28,17 +40,18 @@ import (
 //    also changes the backing array of the `temps` slice.
 //    We don't want that.
 //
-//  Only allow `main()` to change the part of the `temps`
+//    `main()` can change the part of the `temps` slice
-//  slice that is returned from the `Read()`. It shouldn't
+//    that is returned from the `Read()`, but it shouldn't
-//  change the rest of the `temps`.
+//    be able to change the elements in the rest of the
-//
+//    `temps`.
-//  Remember: `received` and `temps` share the same
-//  backing array.
 //
 //
-// NOTE
+//  WHAT YOU NEED TO DO?
 //
-//   You need to import the api package.
+//    So you need to limit the capacity of the returned
+//    slice somehow. Remember: `received` and `temps`
+//    share the same backing array. So, appending to it
+//    can overwrite the same backing array.
 //
 //
 // CURRENT

16-slices/exercises/24-fix-the-memory-leak/hints.md

@@ -0,0 +1,16 @@
+# Hints
+
++ `millions` slice's backing array uses 65 MB of memory.
+
++ `make` a new slice with 10 elements with a new backing array.
+
+  + `copy` the last 10 elements of the `millions` slice to the new slice.
+
+  + So you will have slice with a new backing array only with 10 elements.
+
+  + Then overwrite the `millions` slice by simply `assigning` `last10` slice to it.
+
++ **Remember:** slice ~= pointer to a backing array.
+
+  If you overwrite the slice, it will lose that
+  pointer. So Go can collect the unused memory.

16-slices/exercises/24-fix-the-memory-leak/main.go

@@ -33,10 +33,10 @@ import (
 //
 //  PROBLEM
 //
-//    `main()` calls `api.Report()`. It reports the current
+//    `main()` calls `api.Report()` that reports the current
 //    memory usage.
 //
-//    After that, it calls `api.Read()`. `api.Read()` returns
+//    After that, `main()` calls `api.Read()` that returns
 //    a slice with 10 millions of elements. But you only need
 //    the last 10 elements of the returned slice.
 //
@@ -87,26 +87,14 @@ import (
 //    Memory leak means: Your program is using unnecessary
 //    computer memory. It doesn't release memory that is
 //    no longer needed.
-//    See this: https://en.wikipedia.org/wiki/Memory_leak
+//
+//    See this for more information:
+//    https://en.wikipedia.org/wiki/Memory_leak
 //
 //
 //  HINTS
 //
-//    Only read this if you get stuck.
+//    Check out `hints.md` file if you get stuck.
-//
-//    + `millions` slice's backing array uses 65 MB of memory.
-//
-//    + Make a new slice with 10 elements, and copy the last
-//      10 elements of the `millions` slice to it. This will
-//      create a new backing array for the new slice only
-//      with 10 elements.
-//
-//      Then overwrite the `millions` slice by simply
-//      assigning `last10` slice to it.
-//
-//      Remember: slice ~= pointer to a backing array.
-//      If you overwrite the slice, it will lose that
-//      pointer. So Go can collect the unused memory.
 //
 // ---------------------------------------------------------
 

16-slices/exercises/25-add-lines/main.go

@@ -16,10 +16,13 @@ import (
 //  So, create a new slice and copy every words into it. Lastly,
 //  after each sentence, add a newline character ('\n').
 //
+//
 // ORIGINAL SLICE:
+//
 //   [yesterday all my troubles seemed so far away now it looks as though they are here to stay oh i believe in yesterday]
 //
 // EXPECTED SLICE (NEW):
+//
 //   [yesterday all my troubles seemed so far \n away now it looks as though they are here to stay \n oh i believe in yesterday \n]
 //
 //

16-slices/exercises/26-print-daily-requests/main.go

@@ -18,9 +18,13 @@ import (
 //  See the `reqs` slice and the steps in the code below.
 //
 //
-// RESTRICTION
+// RESTRICTIONS
 //
-//   Your code should work even if you add to or remove the
+//   1. You need to produce the daily slice, don't just loop
+//      and print the element totals directly. The goal is
+//      gaining more experience in slice operations.
+//
+//   2. Your code should work even if you add to or remove the
 //      existing elements from the `reqs` slice.
 //
 //      For example, after solving the exercise, try it with