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::input;
use num::Num;
use std::cmp;

fn main() {
    input! {
        n: usize,
        k: usize,
        a: [usize; n],
    }

    let max_n = 300_001;
    let mut bit = BIT::new(max_n);

    for &na in &a {
        bit.add(na, 1);
    }

    let mut max = 0;
    for &na in &a {
       let right = cmp::min(na + 2*k,max_n);
       let t = bit.sum(na as isize, right as isize);
       max = cmp::max(t, max);
    }

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


struct BIT<T> {
    pub n: usize,
    pub d: Vec<T>,
}

impl<T> BIT<T>
where
    T: Num + Copy + Clone,
{
    fn new(n: usize) -> Self {
        BIT {
            n: n,
            d: vec![T::zero(); n + 1],
        }
    }

    fn add(&mut self, mut i: usize, x: T) {
        i += 1;
        while i <= self.n {
            self.d[i] = self.d[i] + x;
            i += i & i.wrapping_neg();
        }
    }

    //多分[0, i]の和を求める
    fn sum_one(&self, mut _i: isize) -> T {
        let mut x = T::zero();
        _i += 1;
        let mut i = _i as usize;
        while i != 0 {
            x = x + self.d[i];
            i -= i & i.wrapping_neg();
        }
        x
    }

    // [l, r)の和を求める(rは含まない)
    fn sum(&self, l: isize, r: isize) -> T {
        self.sum_one(r - 1) - self.sum_one(l - 1)
    }
}