1508-range-sum-of-sorted-subarray-sums.rb

# frozen_string_literal: true

# 1508. Range Sum of Sorted Subarray Sums
# Medium
# https://leetcode.com/problems/range-sum-of-sorted-subarray-sums

=begin
You are given the array nums consisting of n positive integers. You computed the sum of all non-empty continuous subarrays from the array and then sorted them in non-decreasing order, creating a new array of n * (n + 1) / 2 numbers.
Return the sum of the numbers from index left to index right (indexed from 1), inclusive, in the new array. Since the answer can be a huge number return it modulo 109 + 7.

Example 1:
Input: nums = [1,2,3,4], n = 4, left = 1, right = 5
Output: 13
Explanation: All subarray sums are 1, 3, 6, 10, 2, 5, 9, 3, 7, 4. After sorting them in non-decreasing order we have the new array [1, 2, 3, 3, 4, 5, 6, 7, 9, 10]. The sum of the numbers from index le = 1 to ri = 5 is 1 + 2 + 3 + 3 + 4 = 13.

Example 2:
Input: nums = [1,2,3,4], n = 4, left = 3, right = 4
Output: 6
Explanation: The given array is the same as example 1. We have the new array [1, 2, 3, 3, 4, 5, 6, 7, 9, 10]. The sum of the numbers from index le = 3 to ri = 4 is 3 + 3 = 6.

Example 3:
Input: nums = [1,2,3,4], n = 4, left = 1, right = 10
Output: 50

Constraints:
* n == nums.length
* 1 <= nums.length <= 1000
* 1 <= nums[i] <= 100
* 1 <= left <= right <= n * (n + 1) / 2
=end

# @param {Integer[]} nums
# @param {Integer} n
# @param {Integer} left
# @param {Integer} right
# @return {Integer}
MOD=10**9 + 7

defrange_sum(nums,n,left,right)
nums
.each_with_index.each_with_object([0])do |(v,idx),res|
res << (sum=res[-idx] + v)
nums.first(idx).each{ |w| res << (sum -= w)}
end
.drop(1).sort[left - 1..right - 1].sum % MOD
end

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

require"test/unit"
classTest_range_sum < Test::Unit::TestCase
deftest_
assert_equal13,range_sum([1,2,3,4],4,1,5)
assert_equal6,range_sum([1,2,3,4],4,3,4)
assert_equal50,range_sum([1,2,3,4],4,1,10)
end
end