【朱迪的LeetCode刷题笔记】1502. Can Make Arithmetic Progression From Sequence

Judie

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

Given an array of numbers arr, 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
-106 <= arr[i] <= 106

Judy
Python merge sort

class Solution(object):
    def canMakeArithmeticProgression(self, arr):
        """
        :type arr: List[int]
        :rtype: bool
        """
        
        def mergesort(arr):
            m = len(arr) // 2
            if m == 0:
                return arr
            return merge(mergesort(arr[:m]), mergesort(arr[m:]))
        
        def merge(a1, a2):
            l1 = len(a1)
            l2 = len(a2)
            i1 = 0
            i2 = 0
            rlst = []
            while i1 < l1 and i2 < l2:
                if a1[i1] < a2[i2]:
                    rlst.append(a1[i1])
                    i1 += 1
                else:
                    rlst.append(a2[i2])
                    i2 += 1
            rlst.extend(a1[i1:])
            rlst.extend(a2[i2:])
            return rlst

        l = len(arr)
        if l <= 2:
            return True
        lst = mergesort(arr)
        diff = lst[1] - lst[0]
        for i in range(2, l):
            if lst[i] - lst[i-1] != diff:
                return False
        return True

Python built_in function sort

class Solution(object):
    def canMakeArithmeticProgression(self, arr):
        """
        :type arr: List[int]
        :rtype: bool
        """

        arr.sort()
        diff = arr[1] - arr[0]
        length = len(arr)
        for i in range(2, length):
            if arr[i] - arr[i-1] != diff:
                return False
        return True