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An implementation of Karatsuba multiplication algorithm in Ruby
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| class Karatsuba | |
| # Multiply two numbers using the Karatsuba | |
| # multiplication algorithm | |
| def multiply(num_1, num_2) | |
| if num_1 < 10 || num_2 < 10 | |
| return num_1 * num_2 | |
| end | |
| m_2 = [num_1.to_s.length, num_2.to_s.length].max/2 | |
| # Split the digit sequences about the middle | |
| high_1, low_1 = num_1.divmod(10**m_2) | |
| high_2, low_2 = num_2.divmod(10**m_2) | |
| # Recursively calculate the product using three | |
| # multiplications of smaller numbers | |
| z_0 = multiply(low_1, low_2) | |
| z_1 = multiply((low_1 + high_1), (low_2 + high_2)) | |
| z_2 = multiply(high_1, high_2) | |
| return (z_2 * 10**(2 * m_2)) + ((z_1 - z_2 - z_0) * 10**(m_2)) + (z_0) | |
| end | |
| end |
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Tests for this class can be found here: https://gist.github.com/diegocasmo/a6ea2f301e8efd5d2c08aefdb08dad41