【leetcode】1502. Can Make Arithmetic Progression From Sequence

题目如下：

Given an array of numbers arr. A sequence of numbers is called an arithmetic progression if the difference between any two consecutive elements is the same.

Return true if the array can be rearranged to form an arithmetic progression, otherwise, return false.

Example 1:

Input: arr = [3,5,1]
Output: true
Explanation: We can reorder the elements as [1,3,5] or [5,3,1] with differences 2 and -2 respectively, 
between each consecutive elements.

Example 2:

Input: arr = [1,2,4]
Output: false
Explanation: There is no way to reorder the elements to obtain an arithmetic progression. 

Constraints:

• 2 <= arr.length <= 1000
• -10^6 <= arr[i] <= 10^6

解题思路：很简单的题目，排好序后依次判断相邻元素的差值即可。

代码如下：

class Solution(object):
    def canMakeArithmeticProgression(self, arr):
        """
        :type arr: List[int]
        :rtype: bool
        """
        arr.sort()
        diff = arr[1] - arr[0]
        for i in range(1,len(arr)-1):
            if diff != arr[i+1] - arr[i]:
                return False
        return True