Create Count Prefix and Suffix Pairs I.py

Author: erjan

Count Prefix and Suffix Pairs I.py

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+'''
+You are given a 0-indexed string array words.
+
+Let's define a boolean function isPrefixAndSuffix that takes two strings, str1 and str2:
+
+isPrefixAndSuffix(str1, str2) returns true if str1 is both a 
+prefix
+ and a 
+suffix
+ of str2, and false otherwise.
+For example, isPrefixAndSuffix("aba", "ababa") is true because "aba" is a prefix of "ababa" and also a suffix, but isPrefixAndSuffix("abc", "abcd") is false.
+
+Return an integer denoting the number of index pairs (i, j) such that i < j, and isPrefixAndSuffix(words[i], words[j]) is true.
+
+'''
+
+class Solution:
+    def countPrefixSuffixPairs(self, words: List[str]) -> int:
+        def helper(w1,w2):
+            return w2.startswith(w1) and w2.endswith(w1)
+
+        n =len(words)
+        res = 0
+        for i in range(n):
+            for j in range(n):
+                if i!=j and i<j and helper(words[i],words[j]):
+                    res+=1
+        return res