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 Rust (1.42.0) (judge verdict: Wrong Answer)

use proconio::{fastout, input};
use std::cmp;

#[fastout]
fn main() {
    input! {
        n: usize,
        k: u64,
        r#as: [u64; n],
    }

    let mut ans = 0;

    let mut unvisited = (0..n).collect::<Vec<_>>();
    while !unvisited.is_empty() {
        let mut cur = 1;
        let mut next = vec![];
        let mut a = r#as[unvisited[0]];

        for &i in &unvisited[1..] {
            if diff(a, r#as[i]) <= k {
                a = r#as[i];
                cur += 1;
            } else {
                next.push(i);
            }
        }

        ans = cmp::max(ans, cur);
        unvisited = next;
    }

    let mut unvisited = (0..n).rev().collect::<Vec<_>>();
    while !unvisited.is_empty() {
        let mut cur = 1;
        let mut next = vec![];
        let mut a = r#as[unvisited[0]];

        for &i in &unvisited[1..] {
            if diff(a, r#as[i]) <= k {
                a = r#as[i];
                cur += 1;
            } else {
                next.push(i);
            }
        }

        ans = cmp::max(ans, cur);
        unvisited = next;
    }

    println!("{}", ans);
}

fn diff(a: u64, b: u64) -> u64 {
    cmp::max(a, b) - cmp::min(a, b)
}