day10: some cleanup

day10/part2/main.go

@@ -10,7 +10,7 @@ import (
 )
 
 /*
-	Overall approach...
+	Overall approach:
 	- need to make a map of some kind
 		make it a slice where each element is a struct
 			- each struct will contain:
@@ -36,8 +36,8 @@ type Asteroid struct {
 
 func main() {
 	// read input.txt file, split it into a slice of lines
-	contents := util.ReadFile("../input.txt") // test/example case @ "./test.txt"
-	stringSlice := strings.Split(contents, "\n")
+	input := util.ReadFile("../input.txt")
+	stringSlice := strings.Split(input, "\n")
 
 	// generate 2D grid of each character from stringSlice
 	inputGrid := make([][]string, len(stringSlice))
@@ -45,18 +45,7 @@ func main() {
 		inputGrid[i] = strings.Split(str, "")
 	}
 
-	//* tests while building the TangetAndDistance function
-	// fmt.Println(trig.TangentAndDistance(13, 11, 0, 11))  // 0 13
-	// fmt.Println(trig.TangentAndDistance(13, 11, 15, 11)) // 180 2
-	// fmt.Println(trig.TangentAndDistance(13, 11, 13, 16)) // 90 5
-	// fmt.Println(trig.TangentAndDistance(13, 11, 13, 9))  // 270 2
-	// fmt.Println(trig.TangentAndDistance(1, 1, 0, 2)) // 45 some sqrt
-	// fmt.Println(trig.TangentAndDistance(1, 1, 2, 2)) // 135 some sqrt
-	// fmt.Println(trig.TangentAndDistance(1, 1, 2, 0)) // 225 some sqrt
-	// fmt.Println(trig.TangentAndDistance(1, 1, 0, 0)) // 315 some sqrt
-
 	allAsteroids := makeAsteroidsSlice(inputGrid)
-	// fmt.Println(allAsteroids)
 
 	// need to start this just to the left of zero to get that as the first input
 	lastDegreeUsed := 359.999999
@@ -105,9 +94,6 @@ func main() {
 			// if we pass over 360, subtract 360
 			lastDegreeUsed -= 360
 		}
-		// fmt.Println(minDegDiff)
-		// fmt.Println("lastAsteroid", i, lastAsteroid)
-		// fmt.Println(indexOfAsteroidToDelete, allAsteroids[indexOfAsteroidToDelete])
 	}
 
 	// print the last used asteroid
@@ -125,13 +111,13 @@ func makeAsteroidsSlice(grid [][]string) []Asteroid {
 			// if an asteroid is found...
 			if element == "#" && !(rowIndex == 13 && colIndex == 11) {
 				// calculate the degree and dist
-				degree, dist := trig.TangentAndDistance(13, 11, rowIndex, colIndex)
+				// degree, dist := trig.TangentAndDistance(13, 11, rowIndex, colIndex)
 				// create an instance of an Asteroid struct and append it to the result slice
 				ast := Asteroid{
 					x:          rowIndex,
 					y:          colIndex,
-					degOffVert: degree,
-					distance:   dist,
+					degOffVert: trig.AngleOffVertical(13, 11, rowIndex, colIndex),
+					distance:   trig.Distance(13, 11, rowIndex, colIndex),
 				}
 				result = append(result, ast)
 			}

day10/part2/test1.txt

@@ -1,20 +0,0 @@
-.#..##.###...#######
-##.############..##.
-.#.######.########.#
-.###.#######.####.#.
-#####.##.#.##.###.##
-..#####..#.#########
-####################
-#.####....###.#.#.##
-##.#################
-#####.##.###..####..
-..######..##.#######
-####.##.####...##..#
-.#####..#.######.###
-##...#.##########...
-#.##########.#######
-.####.#.###.###.#.##
-....##.##.###..#####
-.#.#.###########.###
-#.#.#.#####.####.###
-###.##.####.##.#..##

day10/part2/trig/trig.go

@@ -1,62 +1,40 @@
 package trig
 
-import (
-	"math"
-)
-
-// TangentAndDistance docz
-// startX will "always" be 13
-// startY will "always" be 11
-// 0 <= angleOffVery < 360
-func TangentAndDistance(startX, startY, endX, endY int) (angleOffVert, distance float64) {
-	rise, run := float64(endX)-float64(startX), float64(endY)-float64(startY)
-	// fmt.Println(rise, run)
-
-	// edge cases for verticals
-	if run == 0 && rise < 0 {
-		return 0, -1 * rise // endXY is up
-	}
-	if run == 0 && rise > 0 {
-		return 180, rise // endXY is down
-	}
-
-	// handle left or right?
-	if rise == 0 && run < 0 {
-		return 270, -1 * run // left
-	}
-	if rise == 0 && run > 0 {
-		return 90, run // right
-	}
-
-	// not verticals
-	// calculate return distance
-	distance = rise*rise + run*run
-	distance = math.Sqrt(distance)
-
-	// calculate arctangent which will be in radians
-	// determine quadrent
-	if rise < 0 && run > 0 { // top right
-		angleOffVert = -1 * math.Atan(run/rise) * 180 / math.Pi
-	} else if rise > 0 && run > 0 { // bottom right
-		angleOffVert = 90 + math.Atan(rise/run)*180/math.Pi
-	} else if rise > 0 && run < 0 { // bottom left
-		angleOffVert = 180 + -1*math.Atan(run/rise)*180/math.Pi
-	} else if rise < 0 && run < 0 { // top left
-		angleOffVert = 270 + math.Atan(rise/run)*180/math.Pi
-	}
-
-	return angleOffVert, distance
-}
+import "math"
 
 /*
 AngleOffVertical takes in two 2D points, it calculates the angle
-between the line between then and a vertical line. The angle
-returned is to the right of the vertical, i.e. from the vertical
-and through the (mathematical) first quadrant
+between the line and a vertical line (straight up from origin)
+NOTE: "up"/"top" and "down" are lexically flipped b/c of drawing a grid
+where 0, 0 is the top left corner and higher numbers physically go DOWN
+but lexically increase/go UP 🤦‍♂️
 */
 func AngleOffVertical(startX, startY, endX, endY int) float64 {
+	rise := float64(endX) - float64(startX)
+	run := float64(endY) - float64(startY)
 
-	return 0
+	var angle float64
+	// basically a big if/elseif/else block
+	switch {
+	case run == 0 && rise < 0: // up
+		angle = 0
+	case run == 0 && rise > 0: // down
+		angle = 180
+	case rise == 0 && run < 0: // left
+		angle = 270
+	case rise == 0 && run > 0: // right
+		angle = 90
+	case rise < 0 && run > 0: // top right
+		angle = -1 * math.Atan(run/rise) * 180 / math.Pi
+	case rise > 0 && run > 0: // bottom right
+		angle = 90 + math.Atan(rise/run)*180/math.Pi
+	case rise > 0 && run < 0: // bottom left
+		angle = 180 + -1*math.Atan(run/rise)*180/math.Pi
+	case rise < 0 && run < 0: // top left
+		angle = 270 + math.Atan(rise/run)*180/math.Pi
+	}
+
+	return angle
 }
 
 // Distance calculates the distance between two sets of 2D coordinates via Pythagorean's theorem