1498. Number of Subsequences That Satisfy the Given Sum Condition

Author: remy727

README.md

@@ -166,6 +166,7 @@
 | 1480 | Running Sum of 1d Array | [Ruby](./algorithms/ruby/1480-running-sum-of-1d-array.rb) | Easy |
 | 1491 | Average Salary Excluding the Minimum and Maximum Salary | [Ruby](./algorithms/ruby/1491-average-salary-excluding-the-minimum-and-maximum-salary.rb) | Easy |
 | 1493 | Longest Subarray of 1's After Deleting One Element | [Ruby](./algorithms/ruby/1493-longest-subarray-of-1s-after-deleting-one-element.rb) | Medium |
+| 1498 | Number of Subsequences That Satisfy the Given Sum Condition | [Ruby](./algorithms/ruby/1498-number-of-subsequences-that-satisfy-the-given-sum-condition.rb) | Medium |
 | 1523 | Count Odd Numbers in an Interval Range | [Ruby](./algorithms/ruby/1523-count-odd-numbers-in-an-interval-range.rb) | Easy |
 | 1539 | Kth Missing Positive Number | [Ruby](./algorithms/ruby/1539-kth-missing-positive-number.rb) | Easy |
 | 1579 | Remove Max Number of Edges to Keep Graph Fully Traversable | [Ruby](./algorithms/ruby/1579-remove-max-number-of-edges-to-keep-graph-fully-traversable.rb) | Hard |

algorithms/ruby/1498-number-of-subsequences-that-satisfy-the-given-sum-condition.rb

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+# frozen_string_literal: true
+
+# 1498. Number of Subsequences That Satisfy the Given Sum Condition
+# https://leetcode.com/problems/number-of-subsequences-that-satisfy-the-given-sum-condition
+# Medium
+
+=begin
+You are given an array of integers nums and an integer target.
+
+Return the number of non-empty subsequences of nums such that the sum of the minimum and maximum element on it is less or equal to target. Since the answer may be too large, return it modulo 109 + 7.
+
+Example 1:
+Input: nums = [3,5,6,7], target = 9
+Output: 4
+Explanation: There are 4 subsequences that satisfy the condition.
+[3] -> Min value + max value <= target (3 + 3 <= 9)
+[3,5] -> (3 + 5 <= 9)
+[3,5,6] -> (3 + 6 <= 9)
+[3,6] -> (3 + 6 <= 9)
+
+Example 2:
+Input: nums = [3,3,6,8], target = 10
+Output: 6
+Explanation: There are 6 subsequences that satisfy the condition. (nums can have repeated numbers).
+[3] , [3] , [3,3], [3,6] , [3,6] , [3,3,6]
+
+Example 3:
+Input: nums = [2,3,3,4,6,7], target = 12
+Output: 61
+Explanation: There are 63 non-empty subsequences, two of them do not satisfy the condition ([6,7], [7]).
+Number of valid subsequences (63 - 2 = 61).
+
+Constraints:
+1 <= nums.length <= 105
+1 <= nums[i] <= 106
+1 <= target <= 106
+=end
+
+# @param {Integer[]} nums
+# @param {Integer} target
+# @return {Integer}
+def num_subseq(nums, target)
+  nums.sort!
+
+  result = 0
+
+  nums.each_with_index do |num, index|
+    break if (num * 2) > target
+
+    max_index = (nums.bsearch_index { |num_searched| num_searched > (target - num) } || nums.size) - 1
+    result += 2**(max_index - index)
+  end
+
+  result % (10**9 + 7)
+end
+
+# **************** #
+#       TEST       #
+# **************** #
+
+require "test/unit"
+class Test_num_subseq < Test::Unit::TestCase
+  def test_
+    assert_equal 4, num_subseq([3, 5, 6, 7], 9)
+    assert_equal 6, num_subseq([3, 3, 6, 8], 10)
+    assert_equal 61, num_subseq([2, 3, 3, 4, 6, 7], 12)
+  end
+end