Created
November 5, 2019 05:55
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| # Curious Number | |
| # n-digit number is said to be curious if the last n digits of | |
| # its square are the same as the original number. | |
| # For example, 25^2 = 625 and 76^2 = 5776. | |
| # (Curious numbers are also known as automorphic numbers.) | |
| # An example of 9 digit number: | |
| # 212890625^2 = 45322418212890625 | |
| #Q. Complete the code to return all the curious numbers for n digit | |
| #Write a code in following format | |
| class CuriousNumbers | |
| def initialize(digit) | |
| @digit = digit.abs | |
| end | |
| def execute | |
| (lowest_number..highest_number).filter do |num| | |
| num if potential_number?(num) && curious_number?(num) | |
| end | |
| end | |
| private | |
| def potential_number?(a_num) | |
| [0,1,5,6].include?a_num.digits[0] | |
| end | |
| def curious_number?(a_num) | |
| (a_num**2).to_s[-(a_num.digits.count)..-1].to_i == a_num | |
| end | |
| def lowest_number | |
| lowest = '1' | |
| @digit < 2 && 0 || (@digit - 1).times { lowest+='0'} && lowest.to_i | |
| end | |
| def highest_number | |
| highest = '' | |
| @digit == 0 && 0 || @digit == 1 && 9 || @digit.times { highest += '9'} && highest.to_i | |
| end | |
| end | |
| if __FILE__ == $0 | |
| #puts CuriousNumbers.new(2).execute | |
| #puts Benchmark.measure { CuriousNumbers.new(9).execute } | |
| CuriousNumbers.new(7).execute | |
| end |
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