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hammingcode

By: phillip1882 on May 22nd, 2012  |  syntax: Python  |  size: 1.53 KB  |  hits: 72  |  expires: Never
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  1. def encode(message):
  2.    parity = 1
  3.    while len(message)+parity+1 > 2**parity:
  4.       parity += 1
  5.    for i in range(0,parity):
  6.       message = message[:2**i-1]+"_"+message[2**i-1:]
  7.    check = 0
  8.    while check < parity:
  9.       dist = 2**check
  10.       pos = dist-1
  11.       total = 0
  12.       while pos < len(message):
  13.          for i in range(pos,pos+dist):
  14.             try:
  15.                if message[i] != "_":
  16.                  total += int(message[i])
  17.             except IndexError:
  18.                break
  19.          pos += 2*dist
  20.       if total &1 == 1:
  21.          message = message[:dist-1] +"1" +message[dist:]
  22.       else:
  23.          message = message[:dist-1] +"0" +message[dist:]
  24.       check += 1
  25.    return message
  26.  
  27. def decode(message):
  28.    parity = 1
  29.    while len(message)+parity+1 > 2**parity:
  30.       parity += 1
  31.    check = 0
  32.    wrong = 0
  33.    while check < parity:
  34.       dist = 2**check
  35.       pos = dist-1
  36.       total = 0
  37.       while pos <= len(message):
  38.          for i in range(pos,pos+dist):
  39.             try:
  40.                if message[i] != "_":
  41.                   total += int(message[i])
  42.             except IndexError:
  43.                break
  44.          pos += 2*dist
  45.       if total &1 != 0:
  46.          wrong += dist
  47.       check += 1
  48.    if wrong != 0:
  49.       if message[wrong-1] == "0":
  50.          message = message[:wrong-1] +"1" +message[wrong:]
  51.       else:
  52.          message = message[:wrong-1] +"0" +message[wrong:]
  53.       print("error found, corrected")
  54.    return message
  55. print(encode("100101"))
  56. print(decode("0111001101"))
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