leetcode: solve 'container with most water' problem

leetcode/0011-container-with-most-water/elixir/.formatter.exs

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+# Used by "mix format"
+[
+  inputs: ["{mix,.formatter}.exs", "{config,lib,test}/**/*.{ex,exs}"]
+]

leetcode/0011-container-with-most-water/elixir/.gitignore

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+# The directory Mix will write compiled artifacts to.
+/_build/
+
+# If you run "mix test --cover", coverage assets end up here.
+/cover/
+
+# The directory Mix downloads your dependencies sources to.
+/deps/
+
+# Where third-party dependencies like ExDoc output generated docs.
+/doc/
+
+# Ignore .fetch files in case you like to edit your project deps locally.
+/.fetch
+
+# If the VM crashes, it generates a dump, let's ignore it too.
+erl_crash.dump
+
+# Also ignore archive artifacts (built via "mix archive.build").
+*.ez
+
+# Ignore package tarball (built via "mix hex.build").
+solution-*.tar
+
+# Temporary files, for example, from tests.
+/tmp/

leetcode/0011-container-with-most-water/elixir/lib/solution.ex

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+defmodule Solution do
+  @spec max_area(height :: [integer]) :: integer
+  def max_area(height) do
+    iter(0, height, 0, 0)
+  end
+
+  defp iter(prev, [head | tail], head_idx, max_vol) do
+    if prev >= head do
+      iter(prev, tail, head_idx + 1, max_vol)
+    else
+      max_vol = iter_inner(head, head_idx, tail, head_idx + 1, max_vol)
+      iter(head, tail, head_idx + 1, max_vol)
+    end
+  end
+
+  defp iter(_, [], _, max_vol), do: max_vol
+
+  defp iter_inner(a, a_idx, [head | tail], head_idx, max_vol) do
+    distance = head_idx - a_idx
+    min_height = min(a, head)
+    volume = min_height * distance
+    max_vol = max(max_vol, volume)
+    iter_inner(a, a_idx, tail, head_idx + 1, max_vol)
+  end
+
+  defp iter_inner(_, _, [], _, max_vol), do: max_vol
+end

leetcode/0011-container-with-most-water/elixir/mix.exs

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+defmodule Solution.MixProject do
+  use Mix.Project
+
+  def project do
+    [
+      app: :solution,
+      version: "0.1.0",
+      elixir: "~> 1.16",
+      start_permanent: Mix.env() == :prod,
+      deps: deps()
+    ]
+  end
+
+  # Run "mix help compile.app" to learn about applications.
+  def application do
+    [
+      extra_applications: [:logger]
+    ]
+  end
+
+  # Run "mix help deps" to learn about dependencies.
+  defp deps do
+    [
+      # {:dep_from_hexpm, "~> 0.3.0"},
+      # {:dep_from_git, git: "https://github.com/elixir-lang/my_dep.git", tag: "0.1.0"}
+    ]
+  end
+end

leetcode/0011-container-with-most-water/elixir/test/solution_test.exs

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+defmodule SolutionTest do
+  use ExUnit.Case
+  doctest Solution
+
+  test "example 1" do
+    assert Solution.max_area([1, 8, 6, 2, 5, 4, 8, 3, 7]) == 49
+  end
+
+  test "example 2" do
+    assert Solution.max_area([1, 1]) == 1
+  end
+
+  test "large input" do
+    length = Integer.pow(10, 7)
+    input = Enum.map(1..length, fn _ -> :rand.uniform(10000) end)
+    Solution.max_area(input)
+  end
+end

leetcode/0011-container-with-most-water/elixir/test/test_helper.exs

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+ExUnit.start()

leetcode/0011-container-with-most-water/readme.md

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+# 11. Container With Most Water
+
+[Leetcode](https://leetcode.com/problems/container-with-most-water/)
+
+You are given an integer array height of length n. There are n vertical lines drawn such that the two endpoints of the ith line are (i, 0) and (i, height[i]).
+
+Find two lines that together with the x-axis form a container, such that the container contains the most water.
+
+Return the maximum amount of water a container can store.
+
+Notice that you may not slant the container.