-
Notifications
You must be signed in to change notification settings - Fork 7
/
Program.cs
57 lines (56 loc) · 1.26 KB
/
Program.cs
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
using System;
using System.Collections.Generic;
namespace BusRoutes
{
class Program
{
static void Main(string[] args)
{
int[][] routes = new[]
{
new[] {1, 2, 7},
new[] {3, 6, 7},
};
int source = 1, target = 6;
Console.WriteLine(NumBusesToDestination(routes, source, target));
}
public static int NumBusesToDestination(int[][] routes, int source, int target)
{
if (source == target) return 0;
var stops = new HashSet<int>[routes.Length];
var buses = new Dictionary<int, List<int>>();
for (int i = 0; i < routes.Length; i++)
{
stops[i] = new HashSet<int>(routes[i]);
foreach (var stop in routes[i])
{
if (!buses.ContainsKey(stop))
buses[stop] = new List<int>();
buses[stop].Add(i);
}
}
var queue = new Queue<int[]>();
var takenBuses = new HashSet<int>();
foreach (var bus in buses[source])
{
queue.Enqueue(new []{bus, 1});
takenBuses.Add(bus);
}
while (queue.Count != 0)
{
var cur = queue.Dequeue();
if (stops[cur[0]].Contains(target))
return cur[1];
foreach (var stop in routes[cur[0]])
{
foreach (var bus in buses[stop])
{
if(takenBuses.Add(bus))
queue.Enqueue(new []{bus, cur[1] + 1});
}
}
}
return -1;
}
}
}