1630. Arithmetic Subarrays

#### QUESTION:

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 - s 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]
``````

Constraints:

``````n == nums.length
m == l.length
m == r.length
2 <= n <= 500
1 <= m <= 500
0 <= l[i] < r[i] < n
-10^5 <= nums[i] <= 10^5
``````

1.截取l到r的数组进行排序
2.算出步长
3.循环截取数组查看步长是否一致
4.将步长结果放到result中

#### SOLUTION:

``````class Solution {
func checkArithmeticSubarrays(_ nums: [Int], _ l: [Int], _ r: [Int]) -> [Bool] {
var result:[Bool] = []
for indexRange in l.indices {
var tmpArr = nums[l[indexRange]...r[indexRange]].sorted()
let differenct = tmpArr - tmpArr
var differenceEqual:Bool = true
for index in 0..<tmpArr.count-1 {
if (tmpArr[index+1]-tmpArr[index] != differenct) {
differenceEqual = false
break
}
}
result.append(differenceEqual)
}
return result

}
}
``````
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