Problem:
Score : 400 points

Problem Statement

You are given a sequence A_1, A_2, ..., A_N and an integer K.

Print the maximum possible length of a sequence B that satisfies the following conditions:

B is a (not necessarily continuous) subsequence of A.

For each pair of adjacents elements of B, the absolute difference of the elements is at most K.

Constraints

1 \leq N \leq 300,000

0 \leq A_i \leq 300,000

0 \leq K \leq 300,000

All values in input are integers.

Input

Input is given from Standard Input in the following format:

N K
A_1
A_2
:
A_N

Output

Print the answer.

Sample Input 1

10 3
1
5
4
3
8
6
9
7
2
4

Sample Output 1

7

For example, B = (1, 4, 3, 6, 9, 7, 4) satisfies the conditions.

It is a subsequence of A = (1, 5, 4, 3, 8, 6, 9, 7, 2, 4).

All of the absolute differences between two adjacent elements (|1-4|, |4-3|, |3-6|, |6-9|, |9-7|, |7-4|) are at most K = 3.

Solution in C# (.NET Core 3.1.201) (judge verdict: Wrong Answer)

using System;
using System.Collections.Generic;
using System.Linq;

namespace ConsoleApp3
{
    internal class Class2
    {
        //D
        private static void Main(string[] args)
        {
            var nk = Console.ReadLine().Split(" ").Select(int.Parse).ToArray();
            var n = nk[0];
            var k = nk[1];

            var aArray = Enumerable.Range(0, n)
                .Select(_ => int.Parse(Console.ReadLine()))
                .ToArray();

            var list = new List<int>(n);

            var result = aArray.Select((x, i) => (x, i)).Count(a =>
            {
                var (x, i) = a;
                if (i == 0)
                {
                    list.Add(x);
                    return true;
                }

                if (Math.Abs(x - list.Last()) <= k)
                {
                    list.Add(x);
                    return true;
                }
                else
                    return false;
            });

            Console.WriteLine(result);
        }

        ////E
        //private static void Main(string[] args)
        //{
        //    var nq = Console.ReadLine().Split(" ").Select(int.Parse).ToArray();
        //    var n = nq[0];
        //    var q = nq[1];

        //    var s = string.Concat(Enumerable.Repeat('1', n));

        //    var lrds = Enumerable.Range(0, q)
        //        .Select(_ =>
        //        {
        //            var lrd = Console.ReadLine().Split(" ").Select(int.Parse).ToArray();
        //            return (L: lrd[0] - 1, R: lrd[1] - 1, D: lrd[2]);
        //        })
        //        .ToArray();

        //    var aStringBuilder = new StringBuilder(s);

        //    foreach (var (l, r, d) in lrds)
        //    {
        //        aStringBuilder.Remove(l, r - l + 1);
        //        aStringBuilder.Insert(l, string.Concat(Enumerable.Repeat(d.ToString(), r - l + 1)));
        //    }

        //    aStringBuilder.ToString();

        //    Console.WriteLine(list.DefaultIfEmpty().Max());
        //}
    }
}