@@ -0,0 +1,84 @@
+#!/usr/bin/env python
+# encoding: utf-8
+#
+# Copyright (c) 2020 Vladimir Shurygin.  All rights reserved.
+#
+'''
+Longest Palindromic Substring
+
+Solution:
+    The time complexity can be reduced by storing results of subproblems.
+    We maintain a boolean table[n][n] that is filled in bottom up manner.
+    The value of table[i][j] is true, if the substring is palindrome, otherwise false. To calculate table[i][j], we first 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. Otherwise, the value of table[i][j] is made false.
+    https://www.geeksforgeeks.org/longest-palindrome-substring-set-1/
+
+Given a string s, find the longest palindromic substring in s. You may assume that the maximum length of s is 1000.
+
+Example 1:
+
+Input: "babad"
+Output: "bab"
+Note: "aba" is also a valid answer.
+Example 2:
+
+Input: "cbbd"
+Output: "bb"
+'''
+
+
+def longestPalSubstr(st: str) -> str:
+    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
+    max_length = 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
+            max_length = 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 > max_length:
+                    start = i
+                    max_length = k
+            i = i + 1
+        k = k + 1
+    return st[start: start + max_length]
+
+
+if __name__ == '__main__':
+    actual = longestPalSubstr('babad')
+    print(f'expected=bab; actual={actual}')