move to 2020 fodler

2020/solutions/3/README.md

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+# 3
+
+We can simply parse the forest as an array of strings.
+The trees repeat infinitely to the right, this screams for a good mod.
+This means: `char = row[x % len(row)]`. No complex logic needed
+
+For the second one we simply automate the process and sum up the total.
+We can simply encode the coordinates as a function of the index we are current at.
+
+<details>
+  <summary>Solutions</summary>
+  <ol>
+    <li>252</li>
+    <li>57 * 252 * 64 * 66 * 43 = 2608962048</li>
+  </ol>
+</details>

2020/solutions/3/go/main.go

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+package main
+
+import (
+	"fmt"
+	"io/ioutil"
+	"strings"
+)
+
+const high = rune('#')
+
+type sForest struct {
+	data   [][]bool
+	height int
+	width  int
+}
+
+func (f sForest) at(y, x int) bool {
+	if y >= f.height {
+		return false
+	}
+	return f.data[y][x%f.width]
+}
+
+func (f sForest) traverse(y, x int) int {
+	trees := 0
+	for dy := 0; dy <= f.height; dy++ {
+		tree := f.at(dy*y, dy*x)
+		if tree {
+			trees++
+		}
+	}
+	return trees
+}
+
+func main() {
+	data, _ := ioutil.ReadFile("./solutions/3/data.txt")
+
+	rows := strings.Split(strings.TrimSpace(string(data)), "\n")
+	height, width := len(rows), len(rows[0])
+	d := make([][]bool, height)
+
+	for y, row := range rows {
+		d[y] = make([]bool, width)
+		for x, char := range []rune(row) {
+			d[y][x] = char == high
+		}
+	}
+
+	forest := sForest{
+		data:   d,
+		height: height,
+		width:  width,
+	}
+
+	fmt.Println("Simple: ", forest.traverse(1, 3))
+
+	trees11 := forest.traverse(1, 1)
+	trees13 := forest.traverse(1, 3)
+	trees15 := forest.traverse(1, 5)
+	trees17 := forest.traverse(1, 7)
+	trees21 := forest.traverse(2, 1)
+
+	fmt.Println(trees11, trees13, trees15, trees17, trees21)
+	fmt.Println(trees11 * trees13 * trees15 * trees17 * trees21)
+
+}

2020/solutions/3/python/main.py

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+from typing import Dict
+from os.path import join, dirname
+from functools import reduce
+
+
+class Forest():
+
+    def __init__(self, text: str) -> None:
+        self.text = text.strip().split('\n')
+
+    @property
+    def height(self) -> int:
+        return len(self.text)
+
+    def is_tree_at(self, y: int, x: int) -> bool:
+        if y > self.height:
+            return False
+        row = self.text[y]
+        return row[x % len(row)] == '#'
+
+
+data = join(dirname(__file__), '../data.txt')
+with open(data) as f:
+    forest = Forest(f.read())
+
+    # 1
+    trees: int = 0
+    for y in range(forest.height):
+        is_tree: bool = forest.is_tree_at(y, y*3)
+        if is_tree:
+            trees += 1
+    print(f'Result Simple: {trees}')
+
+    # 2
+    all: Dict[str, int] = {
+        '11': 0,
+        '13': 0,
+        '15': 0,
+        '17': 0,
+        '21': 0,
+    }
+    for i in range(forest.height):
+        for key, value in all.items():
+            dy, dx = map(int, list(key))
+            y = i * dy
+            x = i * dx
+            if forest.is_tree_at(y, x):
+                all[key] += 1
+    total = reduce((lambda x, y: x * y), all.values())
+    print(f'Result Combined: {list(all.values())} = {total}')