[Leetcode][JS] 1630. Arithmetic Subarrays

1630. Arithmetic Subarrays

문제

최소 두 개의 원소로 구성되어있는 경우, 연속적인 두개의 원소의 차이가 동일하면 arithmetic하다고 한다

s[i + 1] - s[i] == s[1] - s[0] 인 경우, artimetic하다

 

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]

 

Constraints:

• 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

---

풀이

• 주어진 배열을 정렬한다
• 첫번째 두 원소의 차이 (s[1] - s[0])가 나머지 원소들의 차이와 동일한지 확인하다
  • 다를 경우, false를 반환
  • 같을 경우, true를 반환

---

코드

/**
 * @param {number[]} nums
 * @param {number[]} l
 * @param {number[]} r
 * @return {boolean[]}
 */
var checkArithmeticSubarrays = function(nums, l, r) {
    const isArthmetic = (start, end) => {
        let arr = nums.slice(start, end + 1)
        arr.sort((x, y) => x - y)
        
        const diff = arr[1] - arr[0]
        for (let i = 0; i < arr.length - 1; i++) {
            if (arr[i + 1] - arr[i] != diff) return false
        }
        return true
    }
    
    const res = []
    for (let i = 0; i < l.length; i++) {
        res.push(isArthmetic(l[i], r[i]))
    }
    
    return res
};