Create 17-Letter-Combinations-of-a-Phone-Number.py

Author: neetcode-gh

17-Letter-Combinations-of-a-Phone-Number.py

@@ -0,0 +1,23 @@
+class Solution:
+    def letterCombinations(self, digits: str) -> List[str]:
+        res = []
+        digitToChar = { "2": "abc",
+                        "3": "def",
+                        "4": "ghi",
+                        "5": "jkl",
+                        "6": "mno",
+                        "7": "qprs",
+                        "8": "tuv",
+                        "9": "wxyz" }
+        
+        def backtrack(i, curStr):
+            if len(curStr) == len(digits):
+                res.append(curStr)
+                return
+            for c in digitToChar[digits[i]]:
+                backtrack(i + 1, curStr + c)
+        
+        if digits:
+            backtrack(0, "")
+        
+        return res