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using System;
using static System.Console;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using Xunit;
namespace AdventOfCode {
public class Day05 {
static int FindRow(string boardingPass, int low, int high) {
if (low == high) {
return low;
}
int midpoint = (high + low) / 2;
if (boardingPass[0] == 'F' || boardingPass[0] == 'L') {
return FindRow(boardingPass.Substring(1), low, midpoint);
} else {
return FindRow(boardingPass.Substring(1), midpoint + 1, high);
}
}
static int FindRow(string boardingPass) {
return FindRow(boardingPass, 0, 127);
}
static int FindColumn(string boardingPass) {
return FindRow(boardingPass.Substring(7), 0, 7);
}
static int FindSeatId(string boardingPass) {
return FindRow(boardingPass) * 8 + FindColumn(boardingPass);
}
static int Part1() {
string[] passes = File.ReadAllLines(Util.RootDir + "day05.txt");
int maxId = 0;
foreach (string boardingPass in passes) {
int id = FindSeatId(boardingPass);
if (id > maxId) {
maxId = id;
}
}
return maxId;
}
static int Part2() {
string[] passes = File.ReadAllLines(Util.RootDir + "day05.txt");
var seatIds = new HashSet<int>();
foreach (string boardingPass in passes) {
int id = FindSeatId(boardingPass);
seatIds.Add(id);
}
for (int i = 1; i < 828; i++) {
if (!seatIds.Contains(i) && seatIds.Contains(i - 1) && seatIds.Contains(i + 1)) {
return i;
}
}
return -1;
}
[Fact]
public static void Test() {
Assert.Equal(44, FindRow("FBFBBFFRLR"));
Assert.Equal(5, FindColumn("FBFBBFFRLR"));
Assert.Equal(357, FindSeatId("FBFBBFFRLR"));
Assert.Equal(567, FindSeatId("BFFFBBFRRR"));
Assert.Equal(119, FindSeatId("FFFBBBFRRR"));
Assert.Equal(820, FindSeatId("BBFFBBFRLL"));
Assert.Equal(828, Part1());
WriteLine(Part2());
}
}
}