2022 day 7

Author: pvainio

2022/go/day7/day7.go

@@ -0,0 +1,96 @@
+package main
+
+import (
+	"fmt"
+	"os"
+	"strings"
+)
+
+func main() {
+	input, _ := os.ReadFile("../../input/day7.txt")
+	root := parseTerminal(string(input))
+	var part1 int
+	root.forEach(func(n *node) {
+		if n.fileSize == 0 && n.size() <= 100000 {
+			part1 += n.size()
+		}
+	})
+	fmt.Printf("part1: %v\n", part1)
+
+	needed := 30000000 - (70000000 - root.size())
+
+	smallest := 70000000
+	root.forEach(func(n *node) {
+		if n.size() >= needed && n.size() < smallest {
+			smallest = n.size()
+		}
+	})
+	fmt.Printf("part2: %v\n", smallest)
+}
+
+type node struct {
+	fileSize int
+	parent   *node
+	nodes    map[string]*node
+}
+
+func parseTerminal(input string) *node {
+	root := newNode(0, nil)
+	cwd := root
+	lines := strings.Split(input, "\n")
+	for _, line := range lines {
+		cwd = cwd.apply(line)
+	}
+	return root
+}
+
+func (n *node) apply(line string) *node {
+	name, size := "", 0
+	if strings.HasPrefix(line, "$ cd ") {
+		return n.cd(line[5:])
+	} else if _, err := fmt.Sscanf(line, "%d %s", &size, &name); err == nil {
+		return n.add(name, size)
+	}
+	return n
+}
+
+func (n *node) cd(name string) *node {
+	if name == "/" && n.parent == nil {
+		return n
+	} else if name == "/" {
+		return n.cd("/")
+	} else if name == ".." {
+		return n.parent
+	}
+	if _, ok := n.nodes[name]; !ok {
+		n.nodes[name] = newNode(0, n)
+	}
+	return n.nodes[name]
+}
+
+func (n *node) add(name string, size int) *node {
+	n.nodes[name] = newNode(size, n)
+	return n
+}
+
+func (n *node) size() int {
+	if n.fileSize > 0 {
+		return n.fileSize
+	}
+	var sum int
+	for _, c := range n.nodes {
+		sum += c.size()
+	}
+	return sum
+}
+
+func newNode(size int, parent *node) *node {
+	return &node{fileSize: size, parent: parent, nodes: make(map[string]*node)}
+}
+
+func (n *node) forEach(f func(*node)) {
+	for _, c := range n.nodes {
+		f(c)
+		c.forEach(f)
+	}
+}