From e571f31daac9cb196e4cabe47cd988267457190c Mon Sep 17 00:00:00 2001
From: fartem <jaman.smlnsk@gmail.com>
Date: Fri, 10 Jan 2025 11:24:52 +0300
Subject: [PATCH] 2025-01-10 v. 7.8.9: added "871. Minimum Number of Refueling
 Stops"

---
 README.md                                     |  1 +
 leetcode-ruby.gemspec                         |  2 +-
 .../871_minimum_number_of_refueling_stops.rb  | 21 +++++++++
 ...t_871_minimum_number_of_refueling_stops.rb | 47 +++++++++++++++++++
 4 files changed, 70 insertions(+), 1 deletion(-)
 create mode 100644 lib/hard/871_minimum_number_of_refueling_stops.rb
 create mode 100644 test/hard/test_871_minimum_number_of_refueling_stops.rb

diff --git a/README.md b/README.md
index 9fc6d442..55051f9f 100644
--- a/README.md
+++ b/README.md
@@ -658,3 +658,4 @@ Profile on LeetCode: [fartem](https://leetcode.com/fartem/).
 | 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)    |
 | 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)        |
diff --git a/leetcode-ruby.gemspec b/leetcode-ruby.gemspec
index f9d5d9ab..0d0ec44e 100644
--- a/leetcode-ruby.gemspec
+++ b/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 = '7.8.8'
+  s.version = '7.8.9'
   s.license = 'MIT'
   s.files = ::Dir['lib/**/*.rb'] + %w[README.md]
   s.executable = 'leetcode-ruby'
diff --git a/lib/hard/871_minimum_number_of_refueling_stops.rb b/lib/hard/871_minimum_number_of_refueling_stops.rb
new file mode 100644
index 00000000..d6e33554
--- /dev/null
+++ b/lib/hard/871_minimum_number_of_refueling_stops.rb
@@ -0,0 +1,21 @@
+# frozen_string_literal: true
+
+# https://leetcode.com/problems/minimum-number-of-refueling-stops/
+# @param {Integer} target
+# @param {Integer} start_fuel
+# @param {Integer[][]} stations
+# @return {Integer}
+def min_refuel_stops(target, start_fuel, stations)
+  dp = ::Array.new(stations.size + 1, 0)
+  dp[0] = start_fuel
+
+  (0...stations.size).each do |i|
+    (0..i).reverse_each do |j|
+      dp[j + 1] = [dp[j + 1], dp[j] + stations[i][1]].max if dp[j] >= stations[i][0]
+    end
+  end
+
+  (0..stations.size).each { |i| return i if dp[i] >= target }
+
+  -1
+end
diff --git a/test/hard/test_871_minimum_number_of_refueling_stops.rb b/test/hard/test_871_minimum_number_of_refueling_stops.rb
new file mode 100644
index 00000000..d44845fa
--- /dev/null
+++ b/test/hard/test_871_minimum_number_of_refueling_stops.rb
@@ -0,0 +1,47 @@
+# frozen_string_literal: true
+
+require_relative '../test_helper'
+require_relative '../../lib/hard/871_minimum_number_of_refueling_stops'
+require 'minitest/autorun'
+
+class MinimumNumberOfRefuelingStopsTest < ::Minitest::Test
+  def test_default_one
+    assert_equal(
+      0,
+      min_refuel_stops(
+        1,
+        1,
+        []
+      )
+    )
+  end
+
+  def test_default_two
+    assert_equal(
+      -1,
+      min_refuel_stops(
+        100,
+        1,
+        [
+          [10, 100]
+        ]
+      )
+    )
+  end
+
+  def test_default_three
+    assert_equal(
+      2,
+      min_refuel_stops(
+        100,
+        10,
+        [
+          [10, 60],
+          [20, 30],
+          [30, 30],
+          [60, 40]
+        ]
+      )
+    )
+  end
+end