Problem: There are N squares arranged in a row from left to right. The height of the i-th square from the left is H_i.  For each square, you will perform either of the following operations once:    * Decrease the height of the square by 1.   * Do nothing.  Determine if it is possible to perform the operations so that the heights of the squares are non-decreasing from left to right.

Submission attempts (in order):
# -*- coding: utf-8 -*-
"""
Created on Sat Apr 20 20:47:47 2019

@author: Owner
"""

import numpy as np
import sys
import collections
import scipy.misc
import math
from operator import itemgetter
import itertools
import copy
import bisect
import heapq


def prime_decomposition(n):
  i = 2
  table = []
  while i * i <= n:
    while n % i == 0:
      n /= i
      table.append(int(i))
    i += 1
  if n > 1:
    table.append(int(n))
  return table   

def digit(i):
    if i > 0:
        return digit(i//10) + [i%10]
    else:
        return []
    
def getNearestValueIndex(list, num):
    

    
    idx = np.abs(np.asarray(list) - num).argmin()
    return idx

def find_index(l, x, default=False):
    if x in l:
        return l.index(x)
    else:
        return default

class UnionFind(object):
    def __init__(self, n=1):
        self.par = [i for i in range(n)]
        self.rank = [0 for _ in range(n)]
        self.size = [1 for _ in range(n)]

    def find(self, x):
        
        if self.par[x] == x:
            return x
        else:
            self.par[x] = self.find(self.par[x])
            return self.par[x]

    def union(self, x, y):
        
        x = self.find(x)
        y = self.find(y)
        if x != y:
            if self.rank[x] < self.rank[y]:
                x, y = y, x
            if self.rank[x] == self.rank[y]:
                self.rank[x] += 1
            self.par[y] = x
            self.size[x] += self.size[y]

    def is_same(self, x, y):
        
        return self.find(x) == self.find(y)

    def get_size(self, x):
        
        x = self.find(x)
        return self.size[x]
    




N = int(input())
H = list(map(int, input().split()))

    
def main(): 
    now = H[0]
    for n, h in enumerate(H):
        if n == 0:
            continue
        else:
            if h-1 < now:
                return print("No")
            elif h == now:
                continue
            else:
                now = h-1
                
            
        
    return print("Yes")
    
                
                
                
            
            
                

    
if __name__ == '__main__':
    main()


# -*- coding: utf-8 -*-
"""
Created on Sat Apr 20 20:47:47 2019

@author: Owner
"""

import numpy as np
import sys
import collections
import scipy.misc
import math
from operator import itemgetter
import itertools
import copy
import bisect
import heapq


def prime_decomposition(n):
  i = 2
  table = []
  while i * i <= n:
    while n % i == 0:
      n /= i
      table.append(int(i))
    i += 1
  if n > 1:
    table.append(int(n))
  return table   

def digit(i):
    if i > 0:
        return digit(i//10) + [i%10]
    else:
        return []
    
def getNearestValueIndex(list, num):
    

    
    idx = np.abs(np.asarray(list) - num).argmin()
    return idx

def find_index(l, x, default=False):
    if x in l:
        return l.index(x)
    else:
        return default

class UnionFind(object):
    def __init__(self, n=1):
        self.par = [i for i in range(n)]
        self.rank = [0 for _ in range(n)]
        self.size = [1 for _ in range(n)]

    def find(self, x):
        
        if self.par[x] == x:
            return x
        else:
            self.par[x] = self.find(self.par[x])
            return self.par[x]

    def union(self, x, y):
        
        x = self.find(x)
        y = self.find(y)
        if x != y:
            if self.rank[x] < self.rank[y]:
                x, y = y, x
            if self.rank[x] == self.rank[y]:
                self.rank[x] += 1
            self.par[y] = x
            self.size[x] += self.size[y]

    def is_same(self, x, y):
        
        return self.find(x) == self.find(y)

    def get_size(self, x):
        
        x = self.find(x)
        return self.size[x]
    




N = int(input())
H = list(map(int, input().split()))

    
def main(): 
    now = H[0]
    for n, h in enumerate(H):
        if n == 0:
            continue
        else:
            if h < now:
                return print("No")
            elif h == now:
                continue
            else:
                now = h-1
                
            
        
    return print("Yes")
    
                
                
                
            
            
                

    
if __name__ == '__main__':
    main()


Verdicts: Wrong Answer

Accepted