So here is a code i have written to find palindromes within a word (To check if there are palindromes within a word including the word itself) Condition: spaces inbetween characters are counted and not ignored Example: A but tuba is a palindrome but technically due to spaces involved now it isn’t. so that’s the criteria.
Based on above, the following code usually should work. You can try on your own with different tests to check out if this code gives any error.
def pal(text):
"""
param text: given string or test
return: returns index of longest palindrome and a list of detected palindromes stored in temp
"""
lst = {}
index = (0, 0)
length = len(text)
if length <= 1:
return index
word = text.lower() # Trying to make the whole string lower case
temp = str()
for x, y in enumerate(word):
# Try to enumerate over the word
t = x
for i in xrange(x):
if i != t+1:
string = word[i:t+1]
if string == string[::-1]:
temp = text[i:t+1]
index = (i, t+1)
lst[temp] = index
tat = lst.keys()
longest = max(tat, key=len)
#print longest
return lst[longest], temp
And here is a defunct version of it. What I mean is I have tried to start out from the middle and detect palindromes by iterating from the beginning and checking for each higher and lower indices for character by checking if they are equal characters. if they are then i am checking if its a palindrome like a regular palindrome check. here’s what I have done
def pal(t):
text = t.lower()
lst = {}
ptr = ''
index = (0, 0)
#mid = len(text)/2
#print mid
dec = 0
inc = 0
for mid, c in enumerate(text):
dec = mid - 1
inc = mid + 1
while dec != 0 and inc != text.index(text[-1]):
print 'dec {}, inc {},'.format(dec, inc)
print 'text[dec:inc+1] {}'.format(text[dec:inc+1])
if dec<0:
dec = 0
if inc > text.index(text[-1]):
inc = text.index(text[-1])
while text[dec] != text[inc]:
flo = findlet(text[inc], text[:dec])
fhi = findlet(text[dec], text[inc:])
if len(flo) != 0 and len(fhi) != 0 and text[flo[-1]] == text[fhi[0]]:
dec = flo[-1]
inc = fhi[0]
print ' break if'
break
elif len(flo) != 0 and text[flo[-1]] == text[inc]:
dec = flo[-1]
print ' break 1st elif'
break
elif len(fhi) != 0 and text[fhi[0]] == text[inc]:
inc = fhi[0]
print ' break 2nd elif'
break
else:
dec -= 1
inc += 1
print ' break else'
break
s = text[dec:inc+1]
print ' s {} '.format(s)
if s == s[::-1]:
index = (dec, inc+1)
lst[s] = index
if dec > 0:
dec -= 1
if inc < text.index(text[-1]):
inc += 1
if len(lst) != 0:
val = lst.keys()
longest = max(val, key = len)
return lst[longest], longest, val
else:
return index
findlet() fun:
def findlet(alpha, string):
f = [i for i,j in enumerate(string) if j == alpha]
return f
Sometimes it works:
pal('madem')
dec -1, inc 1,
text[dec:inc+1]
s m
dec 1, inc 3,
text[dec:inc+1] ade
break 1st elif
s m
dec 2, inc 4,
text[dec:inc+1] dem
break 1st elif
s m
dec 3, inc 5,
text[dec:inc+1] em
break 1st elif
s m
Out[6]: ((0, 1), 'm', ['m'])
pal('Avid diva.')
dec -1, inc 1,
text[dec:inc+1]
break 2nd if
s avid div
dec 1, inc 3,
text[dec:inc+1] vid
break else
s avid
dec 2, inc 4,
text[dec:inc+1] id
break else
s vid d
dec 3, inc 5,
text[dec:inc+1] d d
s d d
dec 2, inc 6,
text[dec:inc+1] id di
s id di
dec 1, inc 7,
text[dec:inc+1] vid div
s vid div
dec 4, inc 6,
text[dec:inc+1] di
break 1st elif
s id di
dec 1, inc 7,
text[dec:inc+1] vid div
s vid div
dec 5, inc 7,
text[dec:inc+1] div
break 1st elif
s vid div
dec 6, inc 8,
text[dec:inc+1] iva
break 1st elif
s avid diva
dec 8, inc 10,
text[dec:inc+1] a.
break else
s va.
dec 6, inc 10,
text[dec:inc+1] iva.
break else
s diva.
dec 4, inc 10,
text[dec:inc+1] diva.
break else
s d diva.
dec 2, inc 10,
text[dec:inc+1] id diva.
break else
s vid diva.
Out[9]: ((0, 9), 'avid diva', ['avid diva', 'd d', 'id di', 'vid div'])
And based on the Criteria/Condition i have put:
pal('A car, a man, a maraca.')
dec -1, inc 1,
text[dec:inc+1]
break else
s
dec -1, inc 3,
text[dec:inc+1]
s a ca
dec 1, inc 3,
text[dec:inc+1] ca
break if
s a ca
dec 2, inc 4,
text[dec:inc+1] car
break else
s car,
dec 3, inc 5,
text[dec:inc+1] ar,
break else
s car,
dec 1, inc 7,
text[dec:inc+1] car, a
break 1st elif
s a car, a
dec 4, inc 6,
text[dec:inc+1] r,
break 1st elif
s car,
dec 5, inc 7,
text[dec:inc+1] , a
break 1st elif
s ar, a
dec 2, inc 8,
text[dec:inc+1] car, a
break 1st elif
s car, a
dec 6, inc 8,
text[dec:inc+1] a
s a
dec 5, inc 9,
text[dec:inc+1] , a m
break else
s r, a ma
dec 3, inc 11,
text[dec:inc+1] ar, a man
break else
s car, a man,
dec 1, inc 13,
text[dec:inc+1] car, a man,
s car, a man,
dec 7, inc 9,
text[dec:inc+1] a m
break else
s a ma
dec 5, inc 11,
text[dec:inc+1] , a man
break else
s r, a man,
dec 3, inc 13,
text[dec:inc+1] ar, a man,
break if
s
dec 8, inc 10,
text[dec:inc+1] ma
break if
s
dec 6, inc 4,
text[dec:inc+1]
break 1st elif
s r
dec 3, inc 5,
text[dec:inc+1] ar,
break else
s car,
dec 1, inc 7,
text[dec:inc+1] car, a
break 1st elif
s a car, a
dec 9, inc 11,
text[dec:inc+1] man
break else
s man,
dec 7, inc 13,
text[dec:inc+1] a man,
break if
s
dec 5, inc 2,
text[dec:inc+1]
break 1st elif
s c
dec 1, inc 3,
text[dec:inc+1] ca
break if
s a ca
dec 10, inc 12,
text[dec:inc+1] an,
break 1st elif
s , a man,
dec 4, inc 13,
text[dec:inc+1] r, a man,
break 1st elif
s car, a man,
dec 11, inc 13,
text[dec:inc+1] n,
break 1st elif
s man,
dec 7, inc 14,
text[dec:inc+1] a man, a
s a man, a
dec 6, inc 15,
text[dec:inc+1] a man, a
s a man, a
dec 5, inc 16,
text[dec:inc+1] , a man, a m
break else
s r, a man, a ma
dec 3, inc 18,
text[dec:inc+1] ar, a man, a mar
break else
s car, a man, a mara
dec 1, inc 20,
text[dec:inc+1] car, a man, a marac
break else
s a car, a man, a maraca
dec 12, inc 14,
text[dec:inc+1] , a
break 1st elif
s an, a
dec 9, inc 15,
text[dec:inc+1] man, a
break if
s
dec 7, inc 2,
text[dec:inc+1]
break 1st elif
s c
dec 1, inc 3,
text[dec:inc+1] ca
break if
s a ca
dec 13, inc 15,
text[dec:inc+1] a
s a
dec 12, inc 16,
text[dec:inc+1] , a m
break 1st elif
s man, a m
dec 8, inc 17,
text[dec:inc+1] man, a ma
break 1st elif
s a man, a ma
dec 6, inc 18,
text[dec:inc+1] a man, a mar
break 1st elif
s r, a man, a mar
dec 3, inc 19,
text[dec:inc+1] ar, a man, a mara
s ar, a man, a mara
dec 2, inc 20,
text[dec:inc+1] car, a man, a marac
s car, a man, a marac
dec 1, inc 21,
text[dec:inc+1] car, a man, a maraca
break 1st elif
s a car, a man, a maraca
dec 14, inc 16,
text[dec:inc+1] a m
break 1st elif
s man, a m
dec 8, inc 17,
text[dec:inc+1] man, a ma
break 1st elif
s a man, a ma
dec 6, inc 18,
text[dec:inc+1] a man, a mar
break 1st elif
s r, a man, a mar
dec 3, inc 19,
text[dec:inc+1] ar, a man, a mara
s ar, a man, a mara
dec 2, inc 20,
text[dec:inc+1] car, a man, a marac
s car, a man, a marac
dec 1, inc 21,
text[dec:inc+1] car, a man, a maraca
break 1st elif
s a car, a man, a maraca
dec 15, inc 17,
text[dec:inc+1] ma
break 1st elif
s a ma
dec 13, inc 18,
text[dec:inc+1] a mar
break 1st elif
s r, a man, a mar
dec 3, inc 19,
text[dec:inc+1] ar, a man, a mara
s ar, a man, a mara
dec 2, inc 20,
text[dec:inc+1] car, a man, a marac
s car, a man, a marac
dec 1, inc 21,
text[dec:inc+1] car, a man, a maraca
break 1st elif
s a car, a man, a maraca
dec 16, inc 18,
text[dec:inc+1] mar
break 1st elif
s r, a man, a mar
dec 3, inc 19,
text[dec:inc+1] ar, a man, a mara
s ar, a man, a mara
dec 2, inc 20,
text[dec:inc+1] car, a man, a marac
s car, a man, a marac
dec 1, inc 21,
text[dec:inc+1] car, a man, a maraca
break 1st elif
s a car, a man, a maraca
dec 17, inc 19,
text[dec:inc+1] ara
s ara
dec 16, inc 20,
text[dec:inc+1] marac
break 1st elif
s car, a man, a marac
dec 1, inc 21,
text[dec:inc+1] car, a man, a maraca
break 1st elif
s a car, a man, a maraca
dec 18, inc 20,
text[dec:inc+1] rac
break 1st elif
s car, a man, a marac
dec 1, inc 21,
text[dec:inc+1] car, a man, a maraca
break 1st elif
s a car, a man, a maraca
dec 19, inc 21,
text[dec:inc+1] aca
s aca
dec 21, inc 23,
text[dec:inc+1] a.
break else
s ca.
dec 19, inc 23,
text[dec:inc+1] aca.
break else
s raca.
dec 17, inc 23,
text[dec:inc+1] araca.
break else
s maraca.
dec 15, inc 23,
text[dec:inc+1] maraca.
break else
s a maraca.
dec 13, inc 23,
text[dec:inc+1] a maraca.
break else
s , a maraca.
dec 11, inc 23,
text[dec:inc+1] n, a maraca.
break else
s an, a maraca.
dec 9, inc 23,
text[dec:inc+1] man, a maraca.
break else
s man, a maraca.
dec 7, inc 23,
text[dec:inc+1] a man, a maraca.
break else
s a man, a maraca.
dec 5, inc 23,
text[dec:inc+1] , a man, a maraca.
break else
s r, a man, a maraca.
dec 3, inc 23,
text[dec:inc+1] ar, a man, a maraca.
break else
s car, a man, a maraca.
dec 1, inc 23,
text[dec:inc+1] car, a man, a maraca.
break else
s a car, a man, a maraca.
Out[8]: ((13, 16), ' a ', ['', ' a ', 'c', ' ', 'aca', 'ara', 'r'])
Sometimes, it doesn’t work at all:
pal('madam')
dec -1, inc 1,
text[dec:inc+1]
s m
dec 1, inc 3,
text[dec:inc+1] ada
break 1st elif
s m
dec 2, inc 4,
text[dec:inc+1] dam
break 1st elif
s m
dec 3, inc 5,
text[dec:inc+1] am
break 1st elif
s m
Out[5]: ((0, 1), 'm', ['m'])
Now considering madam is a very nice palindrome it should work and there are many cases which i haven’t tested myself to find out what other legitimate palindromes it doesn’t detect.
Q1: Why is it sometimes not detecting?
Q2: I would like to optimize my second code for that matter. Any inputs?
Q3: What better approach is there for a much much more efficient code than my First code which iterates many a times?
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Answer
Your solution seems a bit complicated to me. Just look at all of the possible substrings and check them individually:
def palindromes(text):
text = text.lower()
results = []
for i in range(len(text)):
for j in range(0, i):
chunk = text[j:i + 1]
if chunk == chunk[::-1]:
results.append(chunk)
return text.index(max(results, key=len)), results
text.index() will only find the first occurrence of the longest palindrome, so if you want the last, replace it with text.rindex().