Explore fun brain teasers to hone your logic, critical thinking, and problem-solving skills. Gain insights into Go and practice to avoid future mistakes.

go.tar.gz

Go lang

Who knew puzzles could be fun? Puzzles and brain teasers are a great way to practice your critical thinking and improve your logic and problem-solving skills. This course provides a basic understanding of Go. The teasers in this course will help you practice what you already know and help avoid future mistakes.

Go Brain Teasers

# Try it yourself ##
Try executing the code below to see the result.

package main

import (
	"fmt"
	"sync"
)

func main() {
	var count int
	var wg sync.WaitGroup

	for i := 0; i < 1_000_000; i++ {
		wg.Add(1)
		go func() {
			defer wg.Done()
			count++
		}()

	}
	wg.Wait()
	fmt.Println(count)
}




# Explanation ##
What we have here is a race condition. We don’t have an atomic operation, which means the code to increment an integer is interrupted mid-operation. Besides, there is the memory barrier. To speed things up, modern computers try to fetch values from a CPU cache before going the long way to the main memory.

We can look at the assembly output of `count.go` by running `go tool compile -S
count.go`. When we do that, we’ll see the code generated for `count++` on
**line 16**:

```
0x0045 00069 (count.go:16) PCDATA $0, $1
0x0045 00069 (count.go:16) PCDATA $1, $4
0x0045 00069 (count.go:16) MOVQ "".&count+56(SP), AX
0x004a 00074 (count.go:16) PCDATA $0, $0
0x004a 00074 (count.go:16) INCQ (AX)

```
The `MOVQ`  instruction will fetch the current value of the counter to the `AX` register. This might come from the memory or from the cache.

The Go toolchain can help detect such race conditions. Both `go run` and `go test` have a `-race` flag to detect race conditions. Try it out yourself:


```
$ go run -race count.go
==================
WARNING: DATA RACE
Read at 0x00c00011a010 by goroutine 8:
main.main.func1()
./code/count.go:16 +0x6c
Previous write at 0x00c00011a010 by goroutine 7:
main.main.func1()
./code/count.go:16 +0x82
Goroutine 8 (running) created at:
main.main()
./code/count.go:14 +0xe4
Goroutine 7 (finished) created at:
main.main()
./code/count.go:14 +0xe4
```
To solve this problem, use a `sync.Mutex` to ensure only one goroutine
updates `count` at a time.

Understand how different packages work in Go. 

Puzzle 22 Explanation: Go Count

Understand how different packages work in Go.

Before We Begin

Puzzles

Wrapping Up

Puzzle 22 Explanation: Go Count

Try it yourself

Explanation