2020 Day 5 Complete

2020/day05/main.go

@@ -0,0 +1,70 @@
+package main
+
+import (
+	"fmt"
+
+	h "git.bullercodeworks.com/brian/adventofcode/helpers"
+)
+
+func main() {
+	inp := h.StdinToStringSlice()
+
+	seats := make(map[int]Seat)
+	var topSeat int
+	for k := range inp {
+		row, col, seat := findSeatFromId(inp[k])
+		seats[seat] = Seat{
+			Row:  row,
+			Col:  col,
+			Seat: seat,
+		}
+		if seat > topSeat {
+			topSeat = seat
+		}
+	}
+	fmt.Println("# Part 1 - Top Seat:", topSeat)
+	for k := range seats {
+		_, tOk := seats[k-1]
+		if !tOk {
+			_, bOk := seats[k-2]
+			if bOk {
+				fmt.Println("# Part 2 - Missing Seat:", k-1)
+				break
+			}
+		}
+	}
+}
+
+type Seat struct {
+	Row  int
+	Col  int
+	Seat int
+}
+
+func findSeatFromId(id string) (int, int, int) {
+	rowBeg := 0
+	rowEnd := 127
+	colBeg := 0
+	colEnd := 7
+	for k := range id {
+		switch id[k] {
+		case 'F', 'B':
+			rowBeg, rowEnd = findChunk(rowBeg, rowEnd, id[k] == 'F')
+		case 'R', 'L':
+			colBeg, colEnd = findChunk(colBeg, colEnd, id[k] == 'L')
+		}
+	}
+
+	return rowBeg, colBeg, (rowBeg * 8) + colBeg
+}
+
+func findChunk(beg, end int, front bool) (int, int) {
+	if beg == end {
+		return beg, beg
+	}
+	if front {
+		return beg, beg + (end-beg)/2
+	} else {
+		return beg + (end-beg)/2 + 1, end
+	}
+}