day 8 part 1 & 2

Author: DWethmar

day08.sh

@@ -0,0 +1,11 @@
+#! /bin/bash
+
+CHALLENGE=day08
+
+go build -o $(pwd)/bin/$CHALLENGE ./$CHALLENGE/*.go
+
+echo "Tests"
+cat $CHALLENGE/input_test_01.txt | bin/$CHALLENGE
+
+echo "Solution"
+cat $CHALLENGE/input.txt | bin/$CHALLENGE

day08/input.txt

@@ -0,0 +1,99 @@
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day08/input_test_01.txt

@@ -0,0 +1,5 @@
+30373
+25512
+65332
+33549
+35390

day08/iterate.go

@@ -0,0 +1,26 @@
+package main
+
+import (
+	"bufio"
+	"io"
+)
+
+type Step int
+
+const (
+	Continue Step = iota
+	Break
+)
+
+// IterateLines iterates over lines in a reader
+// and calls the provided function for each line.
+// if the function returns false, the iteration stops.
+func IterateLines(r io.Reader, f func(s string) Step) (err error) {
+	scanner := bufio.NewScanner(r)
+	for scanner.Scan() {
+		if c := f(scanner.Text()); c == Break {
+			break
+		}
+	}
+	return scanner.Err()
+}

day08/main.go

@@ -0,0 +1,192 @@
+package main
+
+import (
+	"fmt"
+	"io"
+	"os"
+	"strconv"
+)
+
+type Grid [][]int
+
+func (g Grid) Get(x, y int) int { return g[y][x] }
+
+func main() {
+	g, err := CreateGrid(os.Stdin)
+	if err != nil {
+		panic(err)
+	}
+
+	count, err := CountVisibleTrees(g)
+	if err != nil {
+		panic(err)
+	}
+
+	fmt.Printf("part 1: %d\n", count)
+
+	score, err := HighestScenicScore(g)
+	if err != nil {
+		panic(err)
+	}
+
+	fmt.Printf("part 2: %d\n", score)
+}
+
+func CreateGrid(input io.Reader) (grid Grid, err error) {
+	var y int
+	err = IterateLines(input, func(s string) Step {
+		if grid == nil {
+			grid = Grid{}
+
+			for i := 0; i < len(s); i++ {
+				grid = append(grid, make([]int, len(s)))
+			}
+		}
+
+		for x, c := range s {
+			if v, err := strconv.Atoi(string(c)); err == nil {
+				grid[y][x] = v
+			} else {
+				panic(err)
+			}
+		}
+
+		y++
+
+		return Continue
+	})
+
+	return
+}
+
+// CountVisibleTrees counts the number of visible trees
+// in the grid.
+func CountVisibleTrees(grid Grid) (count int, err error) {
+	grideSize := len(grid)
+
+	count = (grideSize * 4) - 4
+
+	// iterate trees (don't do the edges)
+	for y := 1; y < grideSize-1; y++ {
+		for x := 1; x < grideSize-1; x++ {
+			if IsVisibleTree(grid, x, y) {
+				count++
+			}
+		}
+	}
+
+	return
+}
+
+func IsVisibleTree(grid Grid, x, y int) (visible bool) {
+	treeHeight := grid.Get(x, y)
+	visibleSides := 0
+
+	callBack := func(xb, yb int) Step {
+		if t := grid.Get(xb, yb); treeHeight > t {
+			// check if edge
+			if IsEdge(grid, xb, yb) {
+				// if edge then it's visible
+				visibleSides++
+				return Break
+			}
+
+			return Continue
+		}
+
+		return Break
+	}
+
+	// check up
+	WalkGrid(grid, x, y-1, 0, -1, callBack)
+	// check down
+	WalkGrid(grid, x, y+1, 0, 1, callBack)
+	// check left
+	WalkGrid(grid, x-1, y, -1, 0, callBack)
+	// check right
+	WalkGrid(grid, x+1, y, 1, 0, callBack)
+
+	return visibleSides >= 1
+}
+
+func HighestScenicScore(grid Grid) (score int, err error) {
+	grideSize := len(grid)
+
+	for y := 1; y < grideSize; y++ {
+		for x := 1; x < grideSize; x++ {
+			if s := ScenicScore(grid, x, y); s > score {
+				score = s
+			}
+		}
+	}
+
+	return
+}
+
+func IsEdge(grid Grid, x, y int) bool {
+	return x == 0 || y == 0 || x == len(grid)-1 || y == len(grid)-1
+}
+
+func ScenicScore(grid Grid, x, y int) (score int) {
+	treeHeight := grid.Get(x, y)
+
+	lineOfSights := []int{}
+	lineOfSight := 0
+
+	// stop if you reach an edge or at the first tree that is the same height or taller than the tree under consideration.
+	callBack := func(xb, yb int) Step {
+		lineOfSight++
+
+		if t := grid.Get(xb, yb); treeHeight > t {
+			return Continue
+		}
+
+		return Break
+	}
+
+	// check up
+	WalkGrid(grid, x, y-1, 0, -1, callBack)
+	lineOfSights = append(lineOfSights, lineOfSight)
+	lineOfSight = 0
+
+	// check left
+	WalkGrid(grid, x-1, y, -1, 0, callBack)
+	lineOfSights = append(lineOfSights, lineOfSight)
+	lineOfSight = 0
+
+	// check right
+	WalkGrid(grid, x+1, y, 1, 0, callBack)
+	lineOfSights = append(lineOfSights, lineOfSight)
+	lineOfSight = 0
+
+	// check down
+	WalkGrid(grid, x, y+1, 0, 1, callBack)
+	lineOfSights = append(lineOfSights, lineOfSight)
+	lineOfSight = 0
+
+	// fmt.Printf("x: %d, y: %d, lineOfSights: %v \n", x, y, lineOfSights)
+
+	score = lineOfSights[0]
+	for _, l := range lineOfSights[1:] {
+		score *= l
+	}
+
+	return
+}
+
+func WalkGrid(grid Grid, x, y int, dX, dY int, f func(x, y int) Step) (err error) {
+	for {
+		if x < 0 || y < 0 || x >= len(grid) || y >= len(grid) {
+			break
+		}
+
+		if c := f(x, y); c == Break {
+			break
+		}
+
+		x += dX
+		y += dY
+	}
+
+	return
+}