🟡 Solve problem 17

Author: AF2B

swift/17.swift

@@ -0,0 +1,48 @@
+class Solution {
+    let dict: [Character: [String]] = [
+        "2": ["a", "b", "c"],
+        "3": ["d", "e", "f"],
+        "4": ["g", "h", "i"],
+        "5": ["j", "k", "l"],
+        "6": ["m", "n", "o"],
+        "7": ["p", "q", "r", "s"],
+        "8": ["t", "u", "v"],
+        "9": ["w", "x", "y", "z"]
+    ]
+
+    func letterCombinations(_ digits: String) -> [String] {
+        guard digits.count > 0 else {
+            return []
+        }
+
+        let letters = getLetters(digits)
+        return generateCombinations(letters)
+    }
+
+    private func getLetters(_ digits: String) -> [[String]] {
+        var letters: [[String]] = []
+        for digit in digits {
+            if let letter = dict[digit] {
+                letters.append(letter)
+            }
+        }
+        return letters
+    }
+
+    private func generateCombinations(_ letters: [[String]]) -> [String] {
+        var result: [String] = [""]
+        for letterGroup in letters {
+            var newResult: [String] = []
+            for combination in result {
+                for letter in letterGroup {
+                    newResult.append(combination + letter)
+                }
+            }
+            result = newResult
+        }
+        return result
+    }
+}
+
+let solution = Solution()
+print(solution.letterCombinations("23")) // ["ad", "ae", "af", "bd", "be", "bf", "cd", "ce", "cf"]