Working d10p1, bug if I'm on the edges

day10/maze.go

@@ -3,15 +3,35 @@ package main
 import (
 	"bufio"
 	"fmt"
+	"log"
 	"os"
 	"sync"
 	"time"
 )
 
 // Parallel code, global vars
-type Nodes struct {
+type Maze struct {
 	mu        sync.Mutex
-	variable int
+	direction [][]rune
+	steps     int
+}
+
+var fromWhere = map[rune]int8{
+   'N': 0,
+   'S': 1,
+   'W': 2,
+   'E': 3,
+}
+
+var mapDirections = map[rune]int8{
+	'|': 0, // Vertical
+	'-': 1, // Horizontal
+	'L': 2, // North to East
+	'J': 3, // North to West
+	'7': 4, // South to West
+	'F': 5, // South to East
+	'.': 6, // Ground
+	'S': 7, // Start
 }
 
 func check(e error) {
@@ -34,15 +54,138 @@ func timer(name string) func() {
 	}
 }
 
+func (mz *Maze) ChooseFirstDirection(startPoint [2]int) ([2]int, rune) {
+	// For the first step, we don't care about directions, we only need a tile
+	// were we can step on. E.g., if we have a J North of S we CAN'T go. A 7 would
+	// be OK.
+	y := startPoint[0]
+	x := startPoint[1]
+	// If x - 1 (going west), only 1, 2, 5 allowed
+	temp := mapDirections[mz.direction[y][x-1]]
+	if temp == 1 || temp == 2 || temp == 5 {
+    	// We came from East, we also return 'E'
+    	newSpot := [2]int{y,x-1}
+    	return newSpot, 'E'
+    // If x + 1 (going east), only 1, 3, 4 allowed
+	} else if temp := mapDirections[mz.direction[y][x+1]]; temp == 1 || temp == 3 || temp == 4 {
+    	// We came from West
+    	newSpot := [2]int{y,x+1}
+    	return newSpot, 'W'
+  	// If y - 1 (going north), only 0, 4, 5 allowed
+	} else if temp := mapDirections[mz.direction[y-1][x]]; temp == 0 || temp == 4 || temp == 5 {
+    	// We came from South
+    	newSpot := [2]int{y-1,x}
+    	return newSpot, 'S'
+	} else {
+    	log.Fatal("How is this even possible..?")
+	}
+	s := [2]int{0, 0}
+	return s, 'X'
+}
+
+func (mz *Maze) WeGo(loc [2]int, direction rune) ([2]int, rune) {
+    mapDir := fromWhere[direction]
+    y, x := loc[0], loc[1]
+    thisPipe := mapDirections[mz.direction[y][x]]
+    goNorth := [2]int{y-1, x}
+    goSouth := [2]int{y+1, x}
+    goWest := [2]int{y, x-1}
+    goEast := [2]int{y, x+1}
+    switch mapDir {
+        case 0:
+            switch thisPipe {
+                case 0:
+                    return goSouth, 'N'
+                case 2:
+					return goEast, 'W'
+                case 3:
+                    return goWest, 'E'
+            }
+        case 1:
+            switch thisPipe {
+                case 0:
+                    return goNorth, 'S'
+                case 4:
+                    return goWest, 'E'
+                case 5:
+                    return goEast, 'W'
+            }
+        case 2:
+            switch thisPipe {
+                case 1:
+                    return goEast, 'W'
+                case 3:
+					return goNorth, 'S'
+                case 4:
+                    return goSouth, 'N'
+            }
+        case 3:
+            switch thisPipe {
+                case 1:
+                    return goWest, 'E'
+                case 2:
+                    return goNorth, 'S' 
+                case 5:
+                    return goSouth, 'N'
+            }
+    }
+	s := [2]int{0, 0}
+	return s, 'X'
+}
+
+func (mz *Maze) FindPath(startPoint [2]int) {
+    defer timer("FindPath")()
+    y, x := startPoint[0], startPoint[1]
+    nextCheck, direction := mz.ChooseFirstDirection(startPoint)
+    mz.steps++
+    curY, curX := nextCheck[0], nextCheck[1]
+    for {
+        nextCheck, direction = mz.WeGo(nextCheck, direction)
+        curY, curX = nextCheck[0], nextCheck[1]
+        mz.steps++
+        if y == curY && x == curX { break } 
+    }
+}
+
 func main() {
-	file, err := os.Open("./inputs")
+	if len(os.Args) != 2 {
+		fmt.Println("Must provide exactly one argument. It must be a file.")
+		log.Fatal("NOW I WILL SCREAM AND DIE.")
+	}
+	file, err := os.Open(os.Args[1])
 	check(err)
 	defer file.Close()
 
 	lines := make([]string, 0)
 
+	mz := Maze{ steps: 0, }
+
 	scanner := bufio.NewScanner(file)
 	for scanner.Scan() {
 		lines = append(lines, scanner.Text())
 	}
+
+	numColumns := len(lines)
+
+	mz.direction = make([][]rune, numColumns)
+	// Populate the array of directions
+	for i := 0; i < numColumns; i++ {
+		for j := 0; j < len(lines[i]); j++ {
+			mz.direction[i] = append(mz.direction[i], rune(lines[i][j]))
+		}
+	}
+	var startPoint [2]int
+	// Search for the starting point
+	for i := 0; i < numColumns; i++ {
+		for j := 0; j < len(lines[i]); j++ {
+			if mapDirections[mz.direction[i][j]] == 7 {
+				startPoint[0] = i
+				startPoint[1] = j
+			}
+		}
+	}
+	// Going west:  x - 1 | Going east:  x + 1
+	// Going north: y - 1 | Going south: y + 1
+	mz.FindPath(startPoint)
+	fmt.Printf("Number of steps: %d", mz.steps / 2) 
 }