Merge pull request #771 from fartem/417_Pacific_Atlantic_Water_Flow

2024-11-12 v. 7.0.1: added "417. Pacific Atlantic Water Flow"

Author: fartem

README.md

@@ -566,3 +566,4 @@ Profile on LeetCode: [fartem](https://leetcode.com/fartem/).
 | 398. Random Pick Index                                          | [Link](https://leetcode.com/problems/random-pick-index/)                                          | [Link](./lib/medium/398_random_pick_index.rb)                                          | [Link](./test/medium/test_398_random_pick_index.rb)                                          |
 | 400. Nth Digit                                                  | [Link](https://leetcode.com/problems/nth-digit/)                                                  | [Link](./lib/medium/400_nth_digit.rb)                                                  | [Link](./test/medium/test_400_nth_digit.rb)                                                  |
 | 402. Remove K Digits                                            | [Link](https://leetcode.com/problems/remove-k-digits/)                                            | [Link](./lib/medium/402_remove_k_digits.rb)                                            | [Link](./test/medium/test_402_remove_k_digits.rb)                                            |
+| 417. Pacific Atlantic Water Flow                                | [Link](https://leetcode.com/problems/pacific-atlantic-water-flow/)                                | [Link](./lib/medium/417_pacific_atlantic_water_flow.rb)                                | [Link](./test/medium/test_417_pacific_atlantic_water_flow.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 = '7.0.0'
+  s.version = '7.0.1'
   s.license = 'MIT'
   s.files = ::Dir['lib/**/*.rb'] + %w[README.md]
   s.executable = 'leetcode-ruby'

lib/medium/417_pacific_atlantic_water_flow.rb

@@ -0,0 +1,51 @@
+# frozen_string_literal: true
+
+# https://leetcode.com/problems/pacific-atlantic-water-flow/
+# @param {Integer[][]} heights
+# @return {Integer[][]}
+def pacific_atlantic(heights)
+  r = heights.size
+  c = heights.first.size
+
+  atlantic = ::Array.new(r) { ::Array.new(c) }
+  pacific = ::Array.new(r) { ::Array.new(c) }
+
+  (0...r).each do |i|
+    (0...c).each do |j|
+      dfs417(pacific, heights, i, j, 0) if i.zero? || j.zero?
+
+      dfs417(atlantic, heights, i, j, 0) if i == r - 1 || j == c - 1
+    end
+  end
+
+  result = []
+  (0...r).each do |i|
+    (0...c).each do |j|
+      result << [i, j] if atlantic[i][j] && pacific[i][j]
+    end
+  end
+
+  result
+end
+
+private
+
+# @param {Boolean[][]} sea
+# @param {Integer[][]} grid
+# @param {Integer} r
+# @param {Integer} c
+# @param {Integer} prev
+def dfs417(sea, grid, r, c, prev)
+  return if r.negative? || r >= grid.size || c.negative? || c >= grid.first.size
+
+  return if grid[r][c] < prev
+
+  return if sea[r][c]
+
+  sea[r][c] = true
+
+  dfs417(sea, grid, r + 1, c, grid[r][c])
+  dfs417(sea, grid, r - 1, c, grid[r][c])
+  dfs417(sea, grid, r, c + 1, grid[r][c])
+  dfs417(sea, grid, r, c - 1, grid[r][c])
+end

test/medium/test_417_pacific_atlantic_water_flow.rb

@@ -0,0 +1,39 @@
+# frozen_string_literal: true
+
+require_relative '../test_helper'
+require_relative '../../lib/medium/417_pacific_atlantic_water_flow'
+require 'minitest/autorun'
+
+class PacificAtlanticWaterFlowTest < ::Minitest::Test
+  def test_default_one
+    assert_equal(
+      [
+        [0, 4],
+        [1, 3],
+        [1, 4],
+        [2, 2],
+        [3, 0],
+        [3, 1],
+        [4, 0]
+      ],
+      pacific_atlantic(
+        [
+          [1, 2, 2, 3, 5],
+          [3, 2, 3, 4, 4],
+          [2, 4, 5, 3, 1],
+          [6, 7, 1, 4, 5],
+          [5, 1, 1, 2, 4]
+        ]
+      )
+    )
+  end
+
+  def test_default_two
+    assert_equal(
+      [[0, 0]],
+      pacific_atlantic(
+        [[1]]
+      )
+    )
+  end
+end