38 lines
1.2 KiB
Text
38 lines
1.2 KiB
Text
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func add_with_carry(result, addend, addendpos) {
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loop {
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while (result.len < addendpos+1) {
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result.append(0)
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}
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var addend_digits = (addend.to_i + result[addendpos] -> to_s.chars)
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result[addendpos] = addend_digits.pop
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addend_digits.len > 0 || break
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addend = addend_digits.pop
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addendpos++
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}
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}
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func longhand_multiplication(multiplicand, multiplier) {
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var result = []
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var multiplicand_offset = 0
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multiplicand.reverse.each { |multiplicand_digit|
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var multiplier_offset = multiplicand_offset
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multiplier.reverse.each { |multiplier_digit|
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var multiplication_result = (multiplicand_digit.to_i * multiplier_digit.to_i -> to_s)
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var addend_offset = multiplier_offset
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multiplication_result.reverse.each { |result_digit_addend|
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add_with_carry(result, result_digit_addend, addend_offset)
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addend_offset++
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}
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multiplier_offset++
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}
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multiplicand_offset++
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}
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return result.join.reverse
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}
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say longhand_multiplication('18446744073709551616', '18446744073709551616')
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