day1, example

day11/dayEleven.go

@@ -0,0 +1,106 @@
+package day11
+
+import (
+	"fmt"
+	"log"
+	"os"
+	"strings"
+)
+
+func Run() int {
+	fmt.Println("hello day 11")
+
+	filename := "day11/example"
+	bytes, err := os.ReadFile(filename)
+	if err != nil {
+		panic(fmt.Sprint("cannot read file ", filename))
+	}
+
+	text := strings.TrimSpace( string(bytes) )
+	starCoords := make([]StarCoord, 0)
+
+	lines := strings.Split(text, "\n")
+
+	nonEmptyRows := make(map[int]any)
+	nonEmptyCols := make(map[int]any)
+
+	for rowNum, line := range lines {
+		for colNum, symb := range line {
+			if symb == '#' {
+				starCoords = append(starCoords, StarCoord{rowNum, colNum})
+				nonEmptyCols[colNum] = struct{}{}
+				nonEmptyRows[rowNum] = struct{}{}
+			}
+		}
+	}
+
+	emptyRowsAbove := make([]int, len(lines))
+	emptyColsToTheLeft := make([]int, len(lines))
+
+	for rowNum, _ := range lines {
+		if rowNum > 0 {
+			emptyRowsAbove[rowNum] = emptyRowsAbove[rowNum-1]
+		}
+		_, isRowNonempty := nonEmptyRows[rowNum]
+		if !isRowNonempty {
+			emptyRowsAbove[rowNum] += 1
+		}
+	}
+
+	for colNum, _ := range lines[0] {
+		if colNum > 0 {
+			emptyColsToTheLeft[colNum] = emptyColsToTheLeft[colNum-1]
+		}
+		_, isColNonempty := nonEmptyCols[colNum]
+		if !isColNonempty {
+			emptyColsToTheLeft[colNum] += 1
+		}
+	}
+
+	var distanceSum int
+	for i := 0; i < len(starCoords); i++ {
+		for j := i+1; j < len(starCoords); j++ {
+			// calc distance between stars i and j
+			starA := starCoords[i]
+			starB := starCoords[j]
+
+			maxRow := starA.Row
+			minRow := starB.Row
+
+			if maxRow < minRow {
+				maxRow, minRow = minRow, maxRow
+			}
+
+			emptyRowsBetween := emptyRowsAbove[maxRow] - emptyRowsAbove[minRow]
+
+			rowDistance := maxRow - minRow + emptyRowsBetween
+
+			maxCol := starA.Col
+			minCol := starB.Col
+			if maxCol < minCol {
+				maxCol, minCol = minCol, maxCol
+			}
+
+			emptyColsBetween := emptyColsToTheLeft[maxCol] - emptyColsToTheLeft[minCol]
+
+			colDistance := maxCol - minCol + emptyColsBetween
+
+			distance := rowDistance + colDistance
+			log.Printf("between stars %d %+v and %d %+v distance is %n\n", i, j, starA, starB, distance)
+			distanceSum += distance
+		}
+	}
+
+	// oh, i have list of all stars, i can just iterate over them and
+	// only keep rowNums for which there are stars. yeah
+
+	fmt.Println(starCoords)
+	fmt.Println(emptyRowsAbove)
+	fmt.Println(emptyColsToTheLeft)
+
+	return distanceSum
+}
+
+type StarCoord struct {
+	Row, Col int
+}

day11/example

@@ -0,0 +1,10 @@
+...#......
+.......#..
+#.........
+..........
+......#...
+.#........
+.........#
+..........
+.......#..
+#...#.....

main.go

@@ -3,12 +3,12 @@ package main
 import (
 	"log"
 
-	"sunshine.industries/aoc2023/day10"
+	"sunshine.industries/aoc2023/day11"
 )
 
 func main() {
 	log.Print("> starting run:")
 
-	result := day10.Run()
-	log.Printf("day10 result: %d\n****\n", result)
+	result := day11.Run()
+	log.Printf("day11 result: %d\n****\n", result)
 }