# # @ Javier Felipe Toribio 2019-10-11 # # challenge by Mirielle # # Resistor Network # # Resistors are electrical components that # add resistance to a circuit. # In physics, Resistance is measured in ohms # and when they're connected in series, # the total resistance is merely the sum of the # individual resistances: # # Rtotal = R1 + R2 + R3 + ...Rn # # So When resistors are connected # in parallel, the reciprocal of the total # resistance is equal to the sum of the # reciprocals of the individual resistances: # # Rtotal = R1 + R2 + R3 + ...Rn 1/(Rtotal) # = 1/R1 + 1/R2 + 1/R3 + ...1/Rn # # Let's specify that series resistors be # designated by enclosing them in # parentheses, and parallel resistors by # enclosing them in square brackets. # Now we can calculate the equivalent # resistance of the network: # # (2, 3, 6) = 11 ohms [2, 3, 6]= 1 ohm # # Nesting these structures in the same # way tuples and lists are nested allows us # to model complex resistor networks. # # Create a function that takes a nested # network as a string and returns the # equivalent resistance of the network. # Round results to the nearest tenth of an ohm. # # Examples # # resist("(10, [20, 30])") => 22.0 # # 10 in series with [20, 30] in parallel. # # resist("[10, (20, 30)]") => 8.3 # # 10 in parallel with (20, 30) in series. # # resist("([10, 20], (30, 40))") => 76.7 # # [10, 20] in parallel in series with (30, 40) # in series. r # # resist("(1, [12, 4, (1, [10, (2, 8)])])") => 3.0 # # resist("(6, [8, (4, [8, (4, [6, (8, [6, (10, 2)])])])])") => 10 OPEN = /\(|\[/ CLOSED = /\)|\]/ # Convert input string to a list def to_list(input) list = input.gsub(" ","").split(",").map do |i| s = i lst=[] if s.match(OPEN) while s.match(OPEN) lst << s.slice!(0) end lst << s elsif s.match(CLOSED) while s.match(CLOSED) lst.unshift(s.slice!(-1)) end lst.unshift(s) else lst << s end lst end list.flatten end # Calculate ohms of group of resistors def resist(inp,nums,end_symbol) until inp.empty? symbol = inp.shift() case symbol when "(" nums << resist(inp,[],")") when ")" raise if end_symbol != ")" return nums.inject(&:+) when "[" nums << resist(inp,[],"]") when "]" raise if end_symbol != "]" return 1.0/(nums.inject(0.0) {|s,r| s + 1.0/r }) else nums << symbol.to_f end end nums.first.round(1) end test_cases = ["(10, [20, 30])", # 22.0 "[10, (20, 30)]", # 8.3 "([10, 20], (30, 40))", # 76.7 "(1, [12, 4, (1, [10, (2, 8)])])", # 3.0 "(6, [8, (4, [8, (4, [6, (8, [6, (10, 2)])])])])"] # 10 test_cases.each do |input| inp = to_list(input) begin puts("Input : #{input}\nOhms : #{resist(inp,[],"")}\n\n") rescue puts("Resistor brackets malformed") end end

[challenge] resistor network