11.PoisonousPlants.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace Csharp.Advanced.StacksAndQueues
{
    public partial class StacksAndQueues
    {
        public static class _11PoisonousPlants
        {
            public static void Solution()
            {
                var plantsAmount = int.Parse(Console.ReadLine());
                var plants = Console.ReadLine()
                    .Split()
                    .Select(int.Parse)
                    .ToArray();

                var days = new int[plantsAmount];
                var proximityStack = new Stack<int>();

                proximityStack.Push(0);
                for (int i = 1; i < plantsAmount; i++)
                {
                    int maxDays = 0;

                    while (proximityStack.Count > 0
                           && plants[proximityStack.Peek()] >= plants[i])
                    {
                        maxDays = Math.Max(maxDays, days[proximityStack.Pop()]);
                    }

                    if (proximityStack.Count > 0)
                        days[i] = maxDays + 1;

                    proximityStack.Push(i);
                }
                Console.WriteLine(days.Max());
            }
        }
    }
}