📅  最后修改于: 2022-03-11 14:45:04.599000             🧑  作者: Mango
# The value of table[i][j] is true, if the substring is palindrome, otherwise false.
# To calculate table[i][j], check the value of table[i+1][j-1], if the value is true and str[i] is same as str[j], then we make table[i][j] true.
# Python program
import sys
# A utility function to print a
# substring str[low..high]
def printSubStr(st, low, high) :
sys.stdout.write(st[low : high + 1])
sys.stdout.flush()
return ''
# This function prints the longest palindrome
# substring of st[]. It also returns the length
# of the longest palindrome
def longestPalSubstr(st) :
n = len(st) # get length of input string
# table[i][j] will be false if substring
# str[i..j] is not palindrome. Else
# table[i][j] will be true
table = [[0 for x in range(n)] for y
in range(n)]
# All substrings of length 1 are
# palindromes
maxLength = 1
i = 0
while (i < n) :
table[i][i] = True
i = i + 1
# check for sub-string of length 2.
start = 0
i = 0
while i < n - 1 :
if (st[i] == st[i + 1]) :
table[i][i + 1] = True
start = i
maxLength = 2
i = i + 1
# Check for lengths greater than 2.
# k is length of substring
k = 3
while k <= n :
# Fix the starting index
i = 0
while i < (n - k + 1) :
# Get the ending index of
# substring from starting
# index i and length k
j = i + k - 1
# checking for sub-string from
# ith index to jth index iff
# st[i + 1] to st[(j-1)] is a
# palindrome
if (table[i + 1][j - 1] and
st[i] == st[j]) :
table[i][j] = True
if (k > maxLength) :
start = i
maxLength = k
i = i + 1
k = k + 1
print "Longest palindrome substring is: ", printSubStr(st, start,
start + maxLength - 1)
return maxLength # return length of LPS
# Driver program to test above functions
st = "forgeeksskeegfor"
l = longestPalSubstr(st)
print "Length is:", l
# This code is contributed by Nikita Tiwari.