1732-find-the-highest-altitude.rb

# frozen_string_literal: true

# 1732. Find the Highest Altitude
# https://leetcode.com/problems/find-the-highest-altitude
# Easy

=begin
There is a biker going on a road trip. The road trip consists of n + 1 points at different altitudes. The biker starts his trip on point 0 with altitude equal 0.

You are given an integer array gain of length n where gain[i] is the net gain in altitude between points i and i + 1 for all (0 <= i < n). Return the highest altitude of a point.

Example 1:
Input: gain = [-5,1,5,0,-7]
Output: 1
Explanation: The altitudes are [0,-5,-4,1,1,-6]. The highest is 1.

Example 2:
Input: gain = [-4,-3,-2,-1,4,3,2]
Output: 0
Explanation: The altitudes are [0,-4,-7,-9,-10,-6,-3,-1]. The highest is 0.

Constraints:
n == gain.length
1 <= n <= 100
-100 <= gain[i] <= 100
=end

# @param {Integer[]} gain
# @return {Integer}
def largest_altitude(gain)
  prefix = gain.inject([]) { |acc, value| acc << acc.last.to_i + value.to_i }
  max_gain = prefix.max
  max_gain < 0 ? 0 : max_gain
end

# **************** #
#       TEST       #
# **************** #

require "test/unit"
class Test_largest_altitude < Test::Unit::TestCase
  def test_
    assert_equal 1, largest_altitude([-5, 1, 5, 0, -7])
    assert_equal 0, largest_altitude([-4, -3, -2, -1, 4, 3, 2])
  end
end