Create count-prefix-and-suffix-pairs-ii.py

Python/count-prefix-and-suffix-pairs-ii.py

@@ -0,0 +1,23 @@
+# Time:  O(n * l)
+# Space: O(t)
+
+import collections
+
+
+# trie
+class Solution(object):
+    def countPrefixSuffixPairs(self, words):
+        """
+        :type words: List[str]
+        :rtype: int
+        """
+        _trie = lambda: collections.defaultdict(_trie)
+        trie = _trie()
+        result = 0
+        for w in words:
+            curr = trie
+            for i in xrange(len(w)):
+                curr = curr[w[i], w[~i]]
+                result += curr["_cnt"] if "_cnt" in curr else 0
+            curr["_cnt"] = curr["_cnt"]+1 if "_cnt" in curr else 1
+        return result