Add approach

data_structures/arrays/find_the_highest_altitude.rb

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+# Find the Highest Altitude
+
+# 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.
+#
+
+# @param {Integer[]} gain
+# @return {Integer}
+def largest_altitude(gain)
+  arr = [0]
+  points = gain.count
+
+  # calculate altitude array
+  (1..points).each do |pointer|
+    sum = arr[pointer - 1] + gain[pointer - 1]
+    arr.push(sum)
+  end
+
+  # find maximum altitude
+  max = 0
+  arr.each { |i| max = i if max < i }
+  max
+end
+
+gain = [-5, 1, 5, 0, -7]
+largest_altitude(gain)
+# Output: 1
+
+gain = [-4, -3, -2, -1, 4, 3, 2]
+largest_altitude(gain)
+# Output: 0