palindrome pairs problem

Author: Alagappan Maruthappan

palindrome_pairs.py

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+# https://leetcode.com/problems/palindrome-pairs/description/
+
+from collections import defaultdict
+
+
+class Solution:
+    def palindromePairs(self, words):
+        """
+        :type words: List[str]
+        :rtype: List[List[int]]
+        """
+        ans = set()
+        word_map = defaultdict(lambda: None)
+        for i, w in enumerate(words):
+            word_map[w] = i
+        # print(word_map)
+        for i in range(len(words)):
+            l = 0
+            r = 0
+            word = words[i]
+            # print("Word : " + word)
+            while(l <= r):
+                x = word[l:r]
+                # print("small word : " + x)
+                rev_x = x[::-1]
+                x_id = word_map[rev_x]
+                # print("rev id : " + str(x_id))
+                if x_id != None and x_id != i:
+                    # print("Existing rev word : " + rev_x)
+                    new_word = word + rev_x
+                    if new_word == new_word[::-1]:
+                        # print("Palindrome " + new_word)
+                        ans.add((i, x_id))
+                    new_word = rev_x + word
+                    if new_word == new_word[::-1]:
+                        # print("Palindrome " + new_word)
+                        ans.add((x_id, i))
+                if r < len(word):
+                    r += 1
+                else:
+                    l += 1
+        return list(ans)
+
+
+print(Solution().palindromePairs(["a", "b", "c", "ab", "ac", "aa"]))