might be making a mistake starting 2018...

2019/day10/part1/main.go

@@ -0,0 +1,102 @@
+package main
+
+import (
+	"adventofcode/util"
+	"fmt"
+	"strings"
+)
+
+func main() {
+	// need to read the input.txt file and split each line into a slice
+	input := util.ReadFile("../input.txt")
+	stringSlice := strings.Split(input, "\n")
+
+	// split into a 2D grid with each character
+	gridSlice := make([][]string, len(stringSlice))
+	for i, str := range stringSlice {
+		gridSlice[i] = strings.Split(str, "")
+	}
+
+	// will be the final result value
+	var result int
+	var finalCoords [2]int
+	// iterate through entire slice, for each asteroid found, call a helper function
+	for rowIndex, rowSlice := range gridSlice {
+		for colIndex, element := range rowSlice {
+			if element == "#" {
+				// # are "asteroids", . are empty space
+				// helper function will return how many asteroids are "findable" from the current asteroid
+				visibleFromElement := visibleFromAsteroid(gridSlice, rowIndex, colIndex)
+
+				// take max of return of helper function at end of each loop
+				if result < visibleFromElement {
+					result = visibleFromElement
+					finalCoords[0], finalCoords[1] = rowIndex, colIndex
+				}
+			}
+		}
+	}
+
+	// print out the max found
+	fmt.Printf("best asteroid for the station: row[%v] col[%v]\n", finalCoords[0], finalCoords[1]) // [13, 11]
+	fmt.Println("from 13, 11 (y, x)", result)
+}
+
+// helper function will take, x and y coordinates, and the 2D slice
+// will create a two maps of floats to booleans
+//     (one map to cover left side of asteroid, one map to cover right side of asteroid)
+//     so that anything that is blocked will not be double counted
+// and edge case handling for planets vertically above or below the current asteroid
+func visibleFromAsteroid(grid [][]string, row, col int) (result int) {
+	// make the two maps
+	leftMap, rightMap := make(map[float64]bool), make(map[float64]bool)
+	// make the two booleans for up and down. zero value is false
+	var upBool, downBool bool
+
+	// iterate through every element of the grid slices
+	for rowIndex, rowSlice := range grid {
+		for colIndex, element := range rowSlice {
+			// NOTE this control flow is _GROSS_. Better solution in part2 solution
+			// ensure element is an asteroid & not the asteroid that the helper function is being run on
+			if element == "#" && !(row == rowIndex && col == colIndex) {
+				rise := rowIndex - row
+				run := colIndex - col
+
+				// handle if the found asteroid is directly above the inputted row/col asteroid
+				if run == 0 {
+					if rise < 0 {
+						// check down
+						// note that up and down are semantically "flipped" due to the 2 row being "above" the 0 row
+						if !downBool {
+							downBool = true
+							result++
+						}
+					} else {
+						if !upBool {
+							upBool = true
+							result++
+						}
+					}
+				} else {
+					slope := float64(rise) / float64(run)
+					// handle left or right map
+					if run < 0 {
+						// leftMap
+						if _, inLeftMap := leftMap[slope]; !inLeftMap {
+							leftMap[slope] = true
+							result++
+						}
+					} else {
+						// rightMap
+						if _, inRightMap := rightMap[slope]; !inRightMap {
+							rightMap[slope] = true
+							result++
+						}
+					}
+				}
+			}
+		}
+	}
+
+	return result
+}