Algorithms/Python/String/Manachers_Algorithm.py at main · Kumar-laxmi/Algorithms · GitHub

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SIZE=100000+1
P= [0] * (SIZE*2)


# Transform S into new string Q with special characters inserted to avoid bound checking.
defconvertToNewString(s):
newString='@'

foriinrange(len(s)):
newString+='#'+s[i]

newString+='#$'
returnnewString


deflongestPalindromeSubstring(s):
Q=convertToNewString(s)
c, r=0, 0# current center, right limit

foriinrange(1, len(Q) -1):
# find the corresponding letter in the palindrome substring
iMirror=c- (i-c)

ifr>i:
P[i] =min(r-i, P[iMirror])

# expanding around center i
whileQ[i+1+P[i]] ==Q[i-1-P[i]]:
P[i] +=1

# Update c, r in case if the palindrome centered at i expands past r
ifi+P[i] >r:
c=i# next center = i
r=i+P[i]

# Find the longest palindrome length in P
maxPalindrome=0
centerIndex=0

foriinrange(1, len(Q) -1):
ifP[i] >maxPalindrome:
maxPalindrome=P[i]
centerIndex=i

returns[(centerIndex-1-maxPalindrome) //2: (centerIndex-1-maxPalindrome) //2+maxPalindrome]


s=input()
print(longestPalindromeSubstring(s))