Add solution for 2015 day 01

.editorconfig

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+# EditorConfig is awesome: https://EditorConfig.org
+
+# top-most EditorConfig file
+root = true
+
+[*]
+indent_style = space
+indent_size = 4
+end_of_line = lf
+charset = utf-8
+insert_final_newline = true
+trim_trailing_whitespace = true
+
+[*.rb]
+indent_size = 2

2015/day-01/inputs/sample.txt

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+(())
+()()
+(((
+(()(()(
+))(((((
+())
+))(
+)))
+)())())

2015/day-01/main.rb

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+#!/usr/bin/env ruby
+
+require "pathname"
+
+INPUTS = ["inputs/sample.txt", "inputs/puzzle.txt"].map { |x| Pathname(x) }
+
+def match_paren(char)
+    case char
+    when "(" then 1
+    when ")" then -1
+    end
+end
+
+def solve_part_1(content)
+  content.chars.sum { |x| match_paren(x) }
+end
+
+def solve_part_2(content)
+  content.chars.each.with_index(1).reduce(0) do |acc, (char, index)|
+    acc += match_paren(char)
+    return index if acc == -1
+    acc
+  end
+  nil
+end
+
+def main(files)
+  files.each do |file|
+    puts "File: #{file}"
+    file.read.lines do |line|
+      next if line.empty?
+      result = solve_part_1(line.chomp)
+      puts "  Floor: #{result}"
+      result = solve_part_2(line.chomp)
+      puts "  Basement Floor Position: #{result}"
+      puts " -" * 15
+    end
+  end
+end
+
+main(INPUTS)