1630-arithmetic-subarrays.rb

# frozen_string_literal: true

# 1630. Arithmetic Subarrays
# Medium
# https://leetcode.com/problems/arithmetic-subarrays

=begin
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
=end

# @param {Integer[]} nums
# @param {Integer[]} l
# @param {Integer[]} r
# @return {Boolean[]}
def check_arithmetic_subarrays(nums, l, r)
  result = []

  for i in(0).upto(l.size - 1)
    left = l[i]
    right = r[i]
    arr = nums[left..right].sort!
    distence = arr[1] - arr[0]
    arithmetic = true
    for j in(0).upto(arr.size - 2)
      if (arr[j + 1] - arr[j]) != distence
        arithmetic = false
        break
      end
    end
    result << arithmetic
  end

  result
end

# **************** #
#       TEST       #
# **************** #

require "test/unit"
class Test_check_arithmetic_subarrays < Test::Unit::TestCase
  def test_
    assert_equal [true, false, true], check_arithmetic_subarrays(
      [4, 6, 5, 9, 3, 7],
      [0, 0, 2],
      [2, 3, 5]
    )
    assert_equal [false, true, false, false, true, true], check_arithmetic_subarrays(
      [-12, -9, -3, -12, -6, 15, 20, -25, -20, -15, -10],
      [0, 1, 6, 4, 8, 7],
      [4, 4, 9, 7, 9, 10]
    )
  end
end