19位银行IC卡校验位计算

记录一下。

#encoding:utf-8

def get_check_char(input)
	checksum = 0
	input.slice(0,18).chars.reverse.each_with_index do |e,i|
		t = e.to_i
		if i % 2 == 0
			t *= 2
			t -= 9 if t > 9
		end
		checksum += t
	end
	((checksum % 10) == 0 ? 0.to_s : (10 - (checksum % 10)).to_s)
end

def check_valid?(input)
	input.slice(18,1) == get_check_char(input)
end

1.times do |x|
	puts check_valid?('6222600000001111101')
	puts get_check_char('6222600000001111101')
end