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I have an assignment that needs to solve a cryptarithm. But I cant understand the algorithms that I saw in the internet. Could anybody explain how to do this in simple words?

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amiel
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  • What algorithms have you tried? – Anders Lindahl May 15 '11 at 08:31
  • getting all the possible combinations of characters in a string then compute for the sum to solve the cryptarithm. But its very slow – amiel May 15 '11 at 10:42
  • Have you done a frequency analysis of the ciphertext? – Anders Lindahl May 15 '11 at 10:45
  • Giving links to the "algorithms you saw on the internet" would help us a lot. There are lots of different ways to solve these constraint problems, ranging in dificulty and complexity. How familiar are you with backtracking algorithms? – hugomg May 15 '11 at 14:40

2 Answers2

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It's possible to solve this kind of problem with Genetic Algorithm, here is a solution using GA https://github.com/pauloremoli/cryptarithmetic

pauloremoli
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As a general case, most Constraint Satisfaction Algorithms are a two step process, where a guessing (or branching) phase is followed by a deductive phase, where as many assignments as possible are found without guessing. (Think Sudoku, for example)

Example:

  S E N D
  M O R E
M O N E Y

First step: guess D=1 (remaining guesses = ...)

  S E N 1  | D=1
  M O R E
M O N E Y

Guess E = 1 (Remaining guesses = ...)

  S 1 N 1  | D = 1 | E = 1
  M O R 1
M O N 1 Y

We can now deduce that Y = 2 and that the carry value in the second column is 0

      0
  S 1 N 1  | D = 1 | E = 1, Y = 2
  M O R 1
M O N 1 2

When you reach a dead end, backtrack

hugomg
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