描述
A sequence of numbers is called arithmetic if it consists of at least two elements, and the difference between every two consecutive elements is the same. More formally, a sequence s is arithmetic if and only if s[i+1] - s[i] == s[1] - s[0] for all valid i.
For example, these are arithmetic sequences:
1, 3, 5, 7, 9
7, 7, 7, 7
3, -1, -5, -9
The following sequence is not arithmetic:
1, 1, 2, 5, 7
You are given an array of n integers, nums, and two arrays of m integers each, l and r, representing the m range queries, where the ith query is the range [l[i], r[i]]. All the arrays are 0-indexed.
Return a list of boolean elements answer, where answer[i] is true if the subarray nums[l[i]], nums[l[i]+1], ... , nums[r[i]] can be rearranged to form an arithmetic sequence, and false otherwise.
Example 1:
Input: nums = [4,6,5,9,3,7], l = [0,0,2], r = [2,3,5]
Output: [true,false,true]
Explanation:
In the 0th query, the subarray is [4,6,5]. This can be rearranged as [6,5,4], which is an arithmetic sequence.
In the 1st query, the subarray is [4,6,5,9]. This cannot be rearranged as an arithmetic sequence.
In the 2nd query, the subarray is [5,9,3,7]. This can be rearranged as [3,5,7,9], which is an arithmetic sequence.
Example 2:
Input: nums = [-12,-9,-3,-12,-6,15,20,-25,-20,-15,-10], l = [0,1,6,4,8,7], r = [4,4,9,7,9,10]
Output: [false,true,false,false,true,true]
Note:
n == nums.length
m == l.length
m == r.length
2 <= n <= 500
1 <= m <= 500
0 <= l[i] < r[i] < n
-105 <= nums[i] <= 105
解析
根据题意，l[i] 和 r[i] 分别是组成 nums 子数组的左索引和右索引，所以只要同时取得 l[i] 和 r[i] 从 nums 中截取得到子数组，并且对其进行是否为等差序列的判断，最后将布尔结果放入 res 中即可，遍历得到所有的子数组对所有的子数组进行判断后即可得到 res 。
解答
class Solution(object):
def checkArithmeticSubarrays(self, nums, l, r):
"""
:type nums: List[int]
:type l: List[int]
:type r: List[int]
:rtype: List[bool]
"""
res = []
for i in range(len(l)):
l_index = l[i]
r_index = r[i]
tmp = nums[l_index:r_index+1]
tmp.sort()
if(len(tmp)==2):
res.append(True)
continue
distance = tmp[1]-tmp[0]
for j in range(2, len(tmp)):
if distance != tmp[j]-tmp[j-1]:
res.append(False)
break
elif j==len(tmp)-1:
res.append(True)
return res
运行结果
Runtime: 168 ms, faster than 93.02% of Python online submissions for Arithmetic Subarrays.
Memory Usage: 13.4 MB, less than 86.05% of Python online submissions for Arithmetic Subarrays.
原题链接：leetcode.com/problems/ar…
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