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 (Python):

class SegmentTree:
  def __init__(self, n, p, unit, f):
    self.num = 2**((n-1).bit_length())
    self.seg = [unit]*(2*self.num)
    for i in range(n):
      self.seg[i+self.num] = p[i]
    for i in range(self.num-1, 0, -1):
      self.seg[i] = f(self.seg[i << 1], self.seg[(i << 1)+1])
    self.f = f
    self.unit = unit

  def update(self, i, x):
    i += self.num
    self.seg[i] = x
    while i:
      i >>= 1
      self.seg[i] = self.f(self.seg[i << 1], self.seg[(i << 1)+1])

  def query(self, l, r):
    ansl = ansr = self.unit
    l += self.num
    r += self.num-1
    if l == r:
      return self.seg[l]
    while l < r:
      if l & 1:
        ansl = self.f(ansl, self.seg[l])
        l += 1
      if ~r & 1:
        ansr = self.f(self.seg[r], ansr)
        r -= 1
      l >>= 1
      r >>= 1
    if l == r:
      ansl = self.f(ansl, self.seg[l])
    return self.f(ansl, ansr)

n,k=map(int,input().split())
a=[int(input())for _ in range(n)]
m=max(a)
seg=SegmentTree(m,[0]*m,0,lambda x,y: max(x,y))
ans=0
for x in a:
  f=seg.query(max(0,x-k),min(m,x+k)+1)
  seg.update(x,f+1)
  ans=max(ans,f+1)
print(ans)