0332-reconstruct-itinerary.cs

public class Solution {
public IList<string> FindItinerary(IList<IList<string>> tickets)
        {
            var map = new Dictionary<string, List<string>>();
            foreach (var ticket in tickets)
            {
                if (!map.TryGetValue(ticket[0], out var adj))
                {
                    adj = new List<string>();
                    map.Add(ticket[0], adj);
                }
                adj.Add(ticket[1]);
            }

            foreach (var adj in map.Values)
            {
                adj.Sort(Comparer<string>.Create((a, b) => string.Compare(b, a)));
            }

            var res = new Stack<string>();
            DfsVisit(map, "JFK", res);
            return res.ToList();
        }

        private void DfsVisit(Dictionary<string, List<string>> map, string src, Stack<string> ans)
        {
            if (map.TryGetValue(src, out var adj))
            {
                while (adj.Count > 0)
                {
                    var next = adj.Last();
                    adj.RemoveAt(adj.Count - 1);
                    DfsVisit(map, next, ans);
                }
            }
            ans.Push(src);
        }
}