Advent of Code

Overview

"Decided to dive back into Go, and what better way to learn than doing Advent of Code.

Key Takeaways

Stack / Heap Variables declared in a function are often on the stack, while dynamically allocated ones (like slices grown beyond a certain size) go to the heap.

func example() {
    x := 42                // Likely stored on the stack
    largeSlice := make([]int, 1000000) // Allocated on the heap
    fmt.Println(x, largeSlice)
}

Pointer Dereferencing Accessing the value behind a pointer.

func example() {
    x := 42
    ptr := &x            // Pointer to x
    fmt.Println(*ptr)    // Dereferences ptr to access x's value
}

Contiguous Memory Allocation Slices store elements in sequential memory, allowing fast iteration.

func example() {
    nums := []int{1, 2, 3, 4}
    for i, n := range nums {
        fmt.Printf("Index: %d, Value: %d\n", i, n)
    }
}

Slices / Hash Map Slices for ordered data, maps for key-value pairs.

func example() {
    slice := []int{10, 20, 30}
    fmt.Println("Slice:", slice)

    hashMap := map[string]int{"A": 1, "B": 2}
    fmt.Println("Hash Map:", hashMap)
}

Function with Multiple Return Values Returning multiple values directly from a function.

func divide(a, b int) (int, error) {
    if b == 0 {
        return 0, fmt.Errorf("division by zero")
    }
    return a / b, nil
}
func example() {
    result, err := divide(10, 2)
    if err != nil {
        fmt.Println("Error:", err)
    } else {
        fmt.Println("Result:", result)
    }
}

Error Handling Explicit handling of errors using the returned error value.

func readFile(fileName string) error {
    file, err := os.Open(fileName)
    if err != nil {
        return fmt.Errorf("failed to open file: %w", err)
    }
    defer file.Close()
    return nil
}

make and new Allocating slices, maps, and channels with make, and pointers with new.

func example() {
    slice := make([]int, 5)          // Creates a slice with 5 elements
    hashMap := make(map[string]int) // Creates a map
    channel := make(chan int)       // Creates a channel

    ptr := new(int)  // Allocates a pointer to an int initialized to 0
    fmt.Println(slice, hashMap, channel, *ptr)
}

If Special Syntax Declaring and checking variables inline in an if statement.

func example() {
    myMap := map[string]int{"A": 1, "B": 2}
    if value, exists := myMap["A"]; exists {
        fmt.Printf("Found: %d\n", value)
    } else {
        fmt.Println("Not found")
    }
}

lukepaoloni/advent-of-code-2024

Advent of Code

Overview

Key Takeaways