On Fri, Nov 11, 2011 at 1:21 AM, Peter Otten <__pete...@web.de> wrote: > lina wrote: > >> Hi, >> >> I tested the one from >> > http://en.wikibooks.org/wiki/Algorithm_Implementation/Strings/Longest_common_substring >> >> mainly: >> >> #!/usr/bin/python3 >> >> a=['1','2','3','7'] >> >> b=['2','3','7'] >> >> def LongestCommonSubstring(S1, S2): >> M = [[0]*(1+len(S2)) for i in range(1+len(S1))] >> longest, x_longest = 0, 0 >> for x in range(1,1+len(S1)): >> for y in range(1,1+len(S2)): >> M[x][y] = M[x-1][y-1]+1 >> if M[x][y] > longest: >> longest = M[x][y] >> x_longest = x >> else: >> M[x][y] = 0 >> return S1[x_longest-longest:x_longest] >> >> >> if __name__=="__main__": >> print(LongestCommonSubstring(a,b)) >> >> $ python3 LongestCommonSubstring.py >> ['1', '2', '3'] >> >> The results isn't right. > > That's not the code from the site you quote. You messed it up when you tried > to convert it to Python 3 (look for the suspicious 8-space indent) > You are right. also correct it to 4-space indention now. Thanks. > Hint: the function doesn't contain anything specific to Python 2 or 3, apart > from the xrange builtin. If you add the line > > xrange = range
Thanks, I did not realize I could substitute the xrange to range this way. cool. > > to your code the unaltered version will run in Python 3 -- and produce the > correct result: > > $ cat longest_common_substring3.py > xrange = range > > def LongestCommonSubstring(S1, S2): > M = [[0]*(1+len(S2)) for i in xrange(1+len(S1))] > longest, x_longest = 0, 0 > for x in xrange(1,1+len(S1)): > for y in xrange(1,1+len(S2)): > if S1[x-1] == S2[y-1]: I did not understand the code well, and the if S1[x-1] == S2[y-1]: was missing during I was typing ( I did not copy/paste, try to type to enhance the learning) > M[x][y] = M[x-1][y-1] + 1 > if M[x][y]>longest: > longest = M[x][y] > x_longest = x > else: > M[x][y] = 0 > return S1[x_longest-longest: x_longest] > > if __name__ == "__main__": > a = ['1','2','3','7'] > b = ['2','3','7'] > > print(LongestCommonSubstring(a, b)) > $ python3 longest_common_substring3.py > ['2', '3', '7'] > > > _______________________________________________ > Tutor maillist - Tutor@python.org > To unsubscribe or change subscription options: > http://mail.python.org/mailman/listinfo/tutor > _______________________________________________ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
