A `Nice array` is defined to be an array where for every value `n` in the array, there is also an element `n-1` or `n+1` in the array.

example:

```
[2,10,9,3] is Nice array because

2=3-1
10=9+1
3=2+1
9=10-1
```
Write a function named `isNice`/`IsNice` that returns `true` if its array argument is a Nice array, else `false`. You should also return `false` if `input` array has `no` elements.

Difficulty: introductory

Starter code:

def is_nice(arr):
	

Solutions:
def is_nice(arr):
    s = set(arr)
    return bool(arr) and all( n+1 in s or n-1 in s for n in s)

def is_nice(arr):
    return all(x+1 in arr or x-1 in arr for x in arr) and len(arr)>0

def is_nice(arr):
    for x in arr:
        if x + 1 not in arr and x - 1 not in arr:
            return False
    return True and len(arr) > 0

def is_nice(arr):
    return len(arr) > 0 and all(n-1 in arr or n+1 in arr for n in arr)

is_nice=lambda l:l!=[]and[e for e in l if(e-1not in l and e+1not in l)]==[]

def is_nice(arr):
    if len(arr) == 0:
        return False
    for n in arr:
        if n-1 not in arr and n+1 not in arr:
            return False
    return True

def is_nice(arr):
    if arr==[]:
       return False
    else:   
        for i in arr:
            if i+1 not in arr:
               if i-1 not in arr:
                    return False
        return True 


def is_nice(arr):
    if not arr: return False
    
    for x in arr:
        if x-1 not in arr and x+1 not in arr:       
            return False
    return True

def is_nice(arr):
    return all(i+1 in arr or i-1 in arr for i in arr) if arr else False

def is_nice(a):
    return all(e + 1 in a or e - 1 in a for e in a) if a else False