Day 5: Part 1 and 2

five/day_five.go

@@ -0,0 +1,104 @@
+package five
+
+import (
+	"bufio"
+	"fmt"
+	"os"
+	"sort"
+)
+
+type pass struct {
+	raw             string
+	row, column, id int
+}
+
+type plane struct {
+	passes []pass
+}
+
+func decode(pass string) (row, column, id int) {
+	rowString := pass[:7]
+	seatString := pass[7:]
+
+	rowMin, rowMax := 0, 127
+	for _, r := range rowString {
+		diff := ((rowMax - rowMin) / 2) + 1
+		switch string(r) {
+		case "F":
+			row = rowMin
+			rowMax -= diff
+		case "B":
+			row = rowMax
+			rowMin += diff
+		}
+	}
+
+	colMin, colMax := 0, 7
+	for _, r := range seatString {
+		diff := ((colMax - colMin) / 2) + 1
+		switch string(r) {
+		case "L":
+			column = colMin
+			colMax -= diff
+		case "R":
+			column = colMax
+			colMin += diff
+		}
+	}
+
+	return row, column, (row*8 + column)
+}
+
+func (p *plane) load(filename string) error {
+	file, err := os.Open(filename)
+	if err != nil {
+		return err
+	}
+	defer file.Close()
+
+	scanner := bufio.NewScanner(file)
+	for scanner.Scan() {
+		row, column, id := decode(scanner.Text())
+		p.passes = append(p.passes, pass{
+			raw:    scanner.Text(),
+			row:    row,
+			column: column,
+			id:     id,
+		})
+	}
+
+	return nil
+}
+
+// PartOne find the highest boarding pass id
+func PartOne() string {
+	plane := plane{}
+	plane.load("five/passes.txt")
+	highestID := 0
+	for _, pass := range plane.passes {
+		if pass.id > highestID {
+			highestID = pass.id
+		}
+	}
+
+	return fmt.Sprintf("The highest seat id is %d on existing passes", highestID)
+}
+
+// PartTwo Find my boarding pass id
+func PartTwo() string {
+	plane := plane{}
+	plane.load("five/passes.txt")
+
+	sort.Slice(plane.passes, func(i, j int) bool {
+		return plane.passes[i].id < plane.passes[j].id
+	})
+	found := 0
+	for i := 0; i < len(plane.passes)-1; i++ {
+		if (plane.passes[i+1].id - plane.passes[i].id) == 2 {
+			found = plane.passes[i].id + 1
+			break
+		}
+	}
+
+	return fmt.Sprintf("My passport id is %d", found)
+}