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  1. # The longest common subsequence in Python
  2.  
  3.  
  4. # Function to find lcs_algo
  5. def lcs_algo(S1, S2, m, n):
  6.     L = [[0 for x in range(n+1)] for x in range(m+1)]
  7.  
  8.     # Building the mtrix in bottom-up way
  9.     for i in range(m+1):
  10.         for j in range(n+1):
  11.             if i == 0 or j == 0:
  12.                 L[i][j] = 0
  13.             elif S1[i-1] == S2[j-1]:
  14.                 L[i][j] = L[i-1][j-1] + 1
  15.             else:
  16.                 L[i][j] = max(L[i-1][j], L[i][j-1])
  17.  
  18.     index = L[m][n]
  19.  
  20.     lcs_algo = [""] * (index+1)
  21.     lcs_algo[index] = ""
  22.  
  23.     i = m
  24.     j = n
  25.     while i > 0 and j > 0:
  26.  
  27.         if S1[i-1] == S2[j-1]:
  28.             lcs_algo[index-1] = S1[i-1]
  29.             i -= 1
  30.             j -= 1
  31.             index -= 1
  32.  
  33.         elif L[i-1][j] > L[i][j-1]:
  34.             i -= 1
  35.         else:
  36.             j -= 1
  37.  
  38.     # Printing the sub sequences
  39.     print("S1 : " + S1 + "\nS2 : " + S2)
  40.     print("LCS: " + "".join(lcs_algo))
  41.  
  42.  
  43. S1 = "ACADB"
  44. S2 = "CBDA"
  45. m = len(S1)
  46. n = len(S2)
  47. lcs_algo(S1, S2, m, n)
Success #stdin #stdout 0.04s 9400KB
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Standard input is empty
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S1 : ACADB
S2 : CBDA
LCS: CB
https://ideone.com/p82MFd
longest common subsequence
language:
Python 3 (python  3.9.5)
created:
292 days ago
visibility:
secret

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