2025-01-19 v. 8.1.7: added "407. Trapping Rain Water II"

Author: fartem

README.md

@@ -676,6 +676,7 @@ Profile on LeetCode: [fartem](https://leetcode.com/fartem/).
 | 297. Serialize and Deserialize Binary Tree                    | [Link](https://leetcode.com/problems/serialize-and-deserialize-binary-tree/)                   | [Link](./lib/hard/297_serialize_and_deserialize_binary_tree.rb)                    | [Link](./test/hard/test_297_serialize_and_deserialize_binary_tree.rb)                    |
 | 336. Palindrome Pairs                                         | [Link](https://leetcode.com/problems/palindrome-pairs/)                                        | [Link](./lib/hard/336_palindrome_pairs.rb)                                         | [Link](./test/hard/test_336_palindrome_pairs.rb)                                         |
 | 363. Max Sum of Rectangle No Larger Than K                    | [Link](https://leetcode.com/problems/max-sum-of-rectangle-no-larger-than-k/)                   | [Link](./lib/hard/363_max_sum_of_rectangle_no_larger_than_k.rb)                    | [Link](./test/hard/test_363_max_sum_of_rectangle_no_larger_than_k.rb)                    |
+| 407. Trapping Rain Water II                                   | [Link](https://leetcode.com/problems/trapping-rain-water-ii/)                                  | [Link](./lib/hard/407_trapping_rain_water_ii.rb)                                   | [Link](./test/hard/test_407_trapping_rain_water_ii.rb)                                   |
 | 458. Poor Pigs                                                | [Link](https://leetcode.com/problems/poor-pigs/)                                               | [Link](./lib/hard/458_poor_pigs.rb)                                                | [Link](./test/hard/test_458_poor_pigs.rb)                                                |
 | 871. Minimum Number of Refueling Stops                        | [Link](https://leetcode.com/problems/minimum-number-of-refueling-stops/)                       | [Link](./lib/hard/871_minimum_number_of_refueling_stops.rb)                        | [Link](./test/hard/test_871_minimum_number_of_refueling_stops.rb)                        |
 | 895. Maximum Frequency Stack                                  | [Link](https://leetcode.com/problems/maximum-frequency-stack/)                                 | [Link](./lib/hard/895_maximum_frequency_stack.rb)                                  | [Link](./test/hard/test_895_maximum_frequency_stack.rb)                                  |

leetcode-ruby.gemspec

@@ -5,7 +5,7 @@ require 'English'
 ::Gem::Specification.new do |s|
   s.required_ruby_version = '>= 3.0'
   s.name = 'leetcode-ruby'
-  s.version = '8.1.6'
+  s.version = '8.1.7'
   s.license = 'MIT'
   s.files = ::Dir['lib/**/*.rb'] + %w[README.md]
   s.executable = 'leetcode-ruby'

lib/hard/407_trapping_rain_water_ii.rb

@@ -0,0 +1,57 @@
+# frozen_string_literal: true
+
+# https://leetcode.com/problems/trapping-rain-water-ii/
+# @param {Integer[][]} height_map
+# @return {Integer}
+def trap_rain_water(height_map)
+  trapped_water = 0
+  water_level_map = ::Array.new(height_map.size) { ::Array.new(height_map[0].size, 20_000) }
+
+  (1...height_map.size - 1).each do |i|
+    water_level_map[i][0] = height_map[i][0]
+
+    (1...height_map[i].size - 1).each { |j| water_level_map[i][j] = 20_000 }
+
+    water_level_map[i][height_map[i].size - 1] = height_map[i][height_map[i].size - 1]
+  end
+
+  (0...height_map[0].size).each do |i|
+    water_level_map[0][i] = height_map[0][i]
+    water_level_map[height_map.size - 1][i] = height_map[height_map.size - 1][i]
+  end
+
+  drain = true
+  while drain
+    drain = false
+    (1...height_map[0].size - 1).each do |i|
+      (1...height_map.size - 1).each do |j|
+        next unless water_level_map[j][i] > height_map[j][i]
+
+        water_level_map[j][i] = [water_level_map[j][i - 1], height_map[j][i]].max if water_level_map[j][i] > water_level_map[j][i - 1]
+        water_level_map[j][i] = [water_level_map[j - 1][i], height_map[j][i]].max if water_level_map[j][i] > water_level_map[j - 1][i]
+      end
+    end
+
+    (height_map[0].size - 2).downto(1) do |i|
+      (height_map.size - 2).downto(1) do |j|
+        next unless water_level_map[j][i] > height_map[j][i]
+
+        water_level_map[j][i] = [water_level_map[j][i + 1], height_map[j][i]].max if water_level_map[j][i] > water_level_map[j][i + 1]
+        water_level_map[j][i] = [water_level_map[j + 1][i], height_map[j][i]].max if water_level_map[j][i] > water_level_map[j + 1][i]
+
+        next unless water_level_map[j][i] < water_level_map[j][i + 1] && water_level_map[j][i + 1] > height_map[j][i + 1] ||
+                    water_level_map[j][i] < water_level_map[j + 1][i] && water_level_map[j + 1][i] > height_map[j + 1][i]
+
+        drain = true
+      end
+    end
+  end
+
+  (1...water_level_map.size - 1).each do |i|
+    (1...water_level_map[i].size - 1).each do |j|
+      trapped_water += water_level_map[i][j] - height_map[i][j]
+    end
+  end
+
+  trapped_water
+end

test/hard/test_407_trapping_rain_water_ii.rb

@@ -0,0 +1,49 @@
+# frozen_string_literal: true
+
+require_relative '../test_helper'
+require_relative '../../lib/hard/407_trapping_rain_water_ii'
+require 'minitest/autorun'
+
+class TrappingRainWaterIITest < ::Minitest::Test
+  def test_default_one
+    assert_equal(
+      4,
+      trap_rain_water(
+        [
+          [1, 4, 3, 1, 3, 2],
+          [3, 2, 1, 3, 2, 4],
+          [2, 3, 3, 2, 3, 1]
+        ]
+      )
+    )
+  end
+
+  def test_default_two
+    assert_equal(
+      10,
+      trap_rain_water(
+        [
+          [3, 3, 3, 3, 3],
+          [3, 2, 2, 2, 3],
+          [3, 2, 1, 2, 3],
+          [3, 2, 2, 2, 3],
+          [3, 3, 3, 3, 3]
+        ]
+      )
+    )
+  end
+
+  def test_additional_one
+    assert_equal(
+      3,
+      trap_rain_water(
+        [
+          [5, 5, 5, 1],
+          [5, 1, 1, 5],
+          [5, 1, 5, 5],
+          [5, 2, 5, 8]
+        ]
+      )
+    )
+  end
+end