Add solution day 9 part 1

Author: terminalnode

solutions/day09/main.go

@@ -1,9 +1,92 @@
 package main
 
 import (
+	"fmt"
 	"github.com/terminalnode/adventofcode2024/common"
 )
 
+type block struct {
+	id   int
+	size int
+}
+
+func (b *block) isFile() bool {
+	return b.id >= 0
+}
+
 func main() {
-	common.Setup(9, nil, nil)
+	common.Setup(9, part1, nil)
+}
+
+func parseBlocks(
+	input string,
+) []block {
+	isFile := true
+	out := make([]block, len(input))
+
+	for idx, c := range input {
+		var id int
+		if isFile {
+			id = idx / 2
+		} else {
+			id = -1
+		}
+
+		out[idx] = block{
+			id:   id,
+			size: int(c - '0'),
+		}
+
+		isFile = !isFile
+	}
+	return out
+}
+
+func part1(
+	input string,
+) string {
+	blocks := parseBlocks(input)
+	sum := 0
+
+	pos := 0
+	for len(blocks) > 0 {
+		b := blocks[0]
+		if b.isFile() {
+			i := 0
+			for i < b.size {
+			}
+		}
+	}
+
+	return fmt.Sprintf("I don't know!")
+}
+
+func popLastBlock(
+	blocks []block,
+) (block, []block) {
+	l := len(blocks)
+	lastIdx := l - 1
+
+	if l <= 1 {
+		// We will panic with array index out of bounds if blocks is 0,
+		// this is on purpose to make errors consistent with go built-ins
+		return blocks[0], []block{}
+	}
+
+	lastBlock := blocks[lastIdx]
+	newBlocks := blocks[:lastIdx]
+	if lastBlock.isFile() {
+		// Last block is a file, all is great
+		return lastBlock, newBlocks
+	}
+
+	// Grab blocks until we get one that is a file
+	trailingSpace := block{id: -1, size: lastBlock.size}
+	l = len(newBlocks)
+	for !lastBlock.isFile() && l > 0 {
+		lastBlock = newBlocks[len(newBlocks)-1]
+		l = len(newBlocks)
+	}
+
+	return lastBlock, newBlocks
 }