I am doing the Leetcode question of Find the Longeest Palindromic Substring .
For example if the input babad then the output can be bab or aba .
OR
if the input is cbbd then the output is bb .
I'm pretty sure I have it figured out, this is my code...
def longestPalindrome(self, s):
n = len(s)
# Empty matrix.
table = [[False for i in range(n)] for j in range(n)]
# Identity matrix.
for i in range(n):
table[i][i] = True
max_len = 0
start = 0
finish = 0
for sil in range(2, n+1):
for i in range(n-sil + 1):
j = sil + i - 1
if sil == 2:
if s[i] == s[j]:
table[i][j] = True
max_len = j-i
start = i
finish = j
else:
if s[i] == s[j] and table[i+1][j-1]:
table[i][j] = True
if (j - i) > finish-start:
max_len = j - i
start = i
finish = j
return s[start:finish+1]
It works on most cases except for when the string is extremely long. I am submitting my code and it is failing on the following case...
"esbtzjaaijqkgmtaajpsdfiqtvxsgfvijpxrvxgfumsuprzlyvhclgkhccmcnquukivlpnjlfteljvykbddtrpmxzcrdqinsnlsteonhcegtkoszzonkwjevlasgjlcquzuhdmmkhfniozhuphcfkeobturbuoefhmtgcvhlsezvkpgfebbdbhiuwdcftenihseorykdguoqotqyscwymtjejpdzqepjkadtftzwebxwyuqwyeegwxhroaaymusddwnjkvsvrwwsmolmidoybsotaqufhepinkkxicvzrgbgsarmizugbvtzfxghkhthzpuetufqvigmyhmlsgfaaqmmlblxbqxpluhaawqkdluwfirfngbhdkjjyfsxglsnakskcbsyafqpwmwmoxjwlhjduayqyzmpkmrjhbqyhongfdxmuwaqgjkcpatgbrqdllbzodnrifvhcfvgbixbwywanivsdjnbrgskyifgvksadvgzzzuogzcukskjxbohofdimkmyqypyuexypwnjlrfpbtkqyngvxjcwvngmilgwbpcsseoywetatfjijsbcekaixvqreelnlmdonknmxerjjhvmqiztsgjkijjtcyetuygqgsikxctvpxrqtuhxreidhwcklkkjayvqdzqqapgdqaapefzjfngdvjsiiivnkfimqkkucltgavwlakcfyhnpgmqxgfyjziliyqhugphhjtlllgtlcsibfdktzhcfuallqlonbsgyyvvyarvaxmchtyrtkgekkmhejwvsuumhcfcyncgeqtltfmhtlsfswaqpmwpjwgvksvazhwyrzwhyjjdbphhjcmurdcgtbvpkhbkpirhysrpcrntetacyfvgjivhaxgpqhbjahruuejdmaghoaquhiafjqaionbrjbjksxaezosxqmncejjptcksnoq"
The error message is Time Limit Exceeded.
Why is this? I am doing a Dynamic Programming solution which should be an accepted answer.
You are not breaking out of your inner loop early, so you are still doing O(n²) work in all cases.
Consider that a palindrome must have either 'xx' or 'x?x' at its center. Where x is any character that appears twice, and ? is any character.
This probably doesn't improve worst case running time for some pathalogical cases, but at least in the example you provided it should save you a lot of computation.
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