排序后迭代比较

class Solution(object):
    def canMakeArithmeticProgression(self, arr):
        """
        :type arr: List[int]
        :rtype: bool
        """
        arr.sort()
        d=arr[1]-arr[0]
        for i in range(2,len(arr)):
            if arr[i]-arr[i-1]!=d:
                return False
        return True