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 (GCC 9.2.1) (judge verdict: Wrong Answer)

#include <stdio.h>
#include <stdlib.h>

int dis (int a, int b) {
    if (a > b) return a - b;
    else return b - a;
}

int max (int a, int b) {
    if (a > b) return a;
    return b;
}

int main (void) {
    int n, k, i, j, r = 0;
    scanf("%d %d", &n, &k);
    int a[n], b[n];
    for (i = 0; i < n; i++) {
        scanf("%d", &a[i]);
        b[i] = 1;
    }

    for (i = 0; i < n - 1; i++) {
        for (j = i + 1; j < n; j++) {
            if (dis(a[i], a[j]) <= k) break;
        }
        if (j < n) {
            b[j] = max(b[j], b[i] + 1);
            r = max(r, b[j]);
        }
    }

    printf("%d\n", r);
    return 0;
}