LPS Algorithm is Added Fixed Issues keon#746 (keon#788)

* Longest Palindromic Subsequence Algorithm is Added * test case added * Renamed

Author: karangadani

README.md

@@ -194,6 +194,7 @@ If you want to uninstall algorithms, it is as simple as:
  - [hashtable](algorithms/map/hashtable.py)
  - [separate_chaining_hashtable](algorithms/map/separate_chaining_hashtable.py)
  - [longest_common_subsequence](algorithms/map/longest_common_subsequence.py)
+ - [longest_palindromic_subsequence](algorithms/map/longest_palindromic_subsequence.py)
  - [randomized_set](algorithms/map/randomized_set.py)
  - [valid_sudoku](algorithms/map/valid_sudoku.py)
  - [word_pattern](algorithms/map/word_pattern.py)

algorithms/map/longest_palindromic_subsequence.py

@@ -0,0 +1,22 @@
+def longest_palindromic_subsequence(str):
+ n = len(str)
+ 
+ # Create a table to store results of subproblems
+ L = [[0 for x in range(n)] for x in range(n)]
+ 
+ for i in range(n):
+ L[i][i] = 1
+ 
+ 
+ for sub_string_length in range(2, n + 1):
+ for i in range(n-sub_string_length + 1):
+ j = i + sub_string_length-1
+ if str[i] == str[j] and sub_string_length == 2:
+ L[i][j] = 2
+ elif str[i] == str[j]:
+ L[i][j] = L[i + 1][j-1] + 2
+ else:
+ L[i][j] = max(L[i][j-1], L[i + 1][j]);
+ 
+ return L[0][n-1]
+

tests/test_map.py

@@ -3,7 +3,8 @@
  Node, SeparateChainingHashTable,
  word_pattern,
  is_isomorphic,
- is_anagram
+ is_anagram,
+ longest_palindromic_subsequence,
 )
 
 import unittest
@@ -164,6 +165,18 @@ def test_is_isomorphic(self):
  self.assertFalse(is_isomorphic("foo", "bar"))
  self.assertTrue(is_isomorphic("paper", "title"))
 
+class TestLongestPalindromicSubsequence(unittest.TestCase):
+ def test_longest_palindromic_subsequence_is_correct(self):
+ self.assertEqual(7,longest_palindromic_subsequence('BBABCBCAB'))
+ self.assertEqual(4,longest_palindromic_subsequence('abbaeae'))
+ self.assertEqual(8,longest_palindromic_subsequence('babbbababaa'))
+ self.assertEqual(6,longest_palindromic_subsequence('daccandeeja'))
+
+ def test_longest_palindromic_subsequence_is_incorrect(self):
+ self.assertEqual(4,longest_palindromic_subsequence('BBABCBCAB'))
+ self.assertEqual(5,longest_palindromic_subsequence('abbaeae'))
+ self.assertEqual(2,longest_palindromic_subsequence('babbbababaa'))
+ self.assertEqual(1,longest_palindromic_subsequence('daccandeeja'))
 
 class TestIsAnagram(unittest.TestCase):
  def test_is_anagram(self):