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Author: wlsgur11

0017-letter-combinations-of-a-phone-number/0017-letter-combinations-of-a-phone-number.py

@@ -0,0 +1,28 @@
+from itertools import permutations
+
+class Solution:
+    def letterCombinations(self, digits: str) -> List[str]:
+        if not digits:
+            return []
+
+        A = {
+            '2': 'abc',
+            '3': 'def',
+            '4': 'ghi',
+            '5': 'jkl',
+            '6': 'mno',
+            '7': 'pqrs',
+            '8': 'tuv',
+            '9': 'wxyz'
+        }
+        
+        def backtrack(combi, next_digits):
+            if len(next_digits) == 0:
+                ans.append(combi)
+            else:
+                for i in A[next_digits[0]]:
+                    backtrack(combi + i, next_digits[1:])
+        
+        ans = []
+        backtrack("", digits)
+        return ans