# Karatsuba Algorithm for Fast Multiplications Part 2.txt -...

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It is very easy to multiply numbers with two digits or less. If one number has ndigits and another number also has n digits, you need n × n multiplications.W = (a + c) × (b + d) – Z – V (one multiplication)Notice that you only need three multiplications in this algorithm. You do not seethat much of a difference because there are only four total digits in 77 × 54.However, if there are 16 or more total digits, reducing the number ofmultiplications has a greater effect.Note that the Karatsuba algorithm has one limitation: it only works with even-numbered total digits. However, this limitation can be easily countered by addingzeros ahead of a number with odd-numbered total digits. For example, the number 354(three digits, odd) can be changed to 0354 (four digits, even).Runtime AnalysisThe conventional multiplication algorithm's complexity is n2, and the Karatsubaalgorithm's complexity is n1.584. The Karatsuba algorithm has a lower complexitydue to the lower number of multiplications needed to calculate the output.
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