var input = File.ReadAllText(Path.Combine(Path.GetDirectoryName(Util.CurrentQueryPath), @"14_input.txt")).Select(c => c-'0').Reverse().ToArray(); var board = new List(); board.Add(3); board.Add(7); int elf1 = 0; int elf2 = 1; for (int gen = 0; ; gen++) { var sum1 = board[elf1] + board[elf2]; if (sum1 >= 10) board.Add(1); board.Add((short)(sum1 % 10)); elf1 = (elf1 + 1 + board[elf1]) % board.Count; elf2 = (elf2 + 1 + board[elf2]) % board.Count; //board.Select((p, i) => (i == elf1) ? $"({p})" : ((i == elf2) ? $"[{p}]" : $" {p} ")).Aggregate((a,b)=>a+" "+b).Dump(); if (board.Count >= input.Length && input.Select((p,i) => board[board.Count-1-i]==p ).All(p=>p)) { (board.Count-input.Length).Dump(); return; } if (board.Count >= input.Length && sum1 >= 10 && input.Select((p, i) => board[board.Count - 2 - i] == p).All(p => p)) { (board.Count - input.Length - 1).Dump(); return; } }