add a solution for 17

fishercoder1534 · fishercoder1534 · commit 3d1ba9357691 · 2022-05-09T07:21:11.000-07:00
diff --git a/src/main/java/com/fishercoder/solutions/_17.java b/src/main/java/com/fishercoder/solutions/_17.java
@@ -37,7 +37,7 @@ List<String> combine(String letters, List<String> result) {
 
     public static class Solution2 {
         /**
-         * My completely solution on 10/11/2021, no backtracking involved.
+         * My completely original solution on 10/11/2021, no backtracking involved.
          */
         public List<String> letterCombinations(String digits) {
             List<String> ans = new ArrayList<>();
@@ -63,4 +63,29 @@ private List<String> recursion(List<String> ans, String[] options, String digits
             return recursion(newAns, options, digits, index + 1);
         }
     }
+
+    public static class Solution3 {
+        /**
+         * My completely original solution on 5/9/2022, no backtracking involved or helper method involved.
+         */
+        public List<String> letterCombinations(String digits) {
+            List<String> ans = new ArrayList<>();
+            if (digits.equals("")) {
+                return ans;
+            }
+            String[] buttons = new String[]{"", "", "abc", "def", "ghi", "jkl", "mno", "pqrs", "tuv", "wxyz"};
+            ans.add("");
+            for (char c : digits.toCharArray()) {
+                String button = buttons[Integer.parseInt(c + "")];
+                List<String> newList = new ArrayList<>();
+                for (String str : ans) {
+                    for (char b : button.toCharArray()) {
+                        newList.add(str + b);
+                    }
+                }
+                ans = newList;
+            }
+            return ans;
+        }
+    }
 }
diff --git a/src/test/java/com/fishercoder/_17Test.java b/src/test/java/com/fishercoder/_17Test.java
@@ -9,19 +9,19 @@
 import java.util.List;
 
 import static org.assertj.core.api.Assertions.assertThat;
-import static org.junit.Assert.assertEquals;
-import static org.junit.Assert.assertTrue;
 
 public class _17Test {
     private static _17.Solution1 solution1;
     private static _17.Solution2 solution2;
+    private static _17.Solution3 solution3;
     private static String digits;
     private static List<String> expected;
 
     @BeforeClass
     public static void setup() {
         solution1 = new _17.Solution1();
         solution2 = new _17.Solution2();
+        solution3 = new _17.Solution3();
     }
 
     @Test
@@ -30,6 +30,7 @@ public void test1() {
         expected = new ArrayList<>(Arrays.asList("a", "b", "c"));
         assertThat(expected).hasSameElementsAs(solution1.letterCombinations(digits));
         assertThat(expected).hasSameElementsAs(solution2.letterCombinations(digits));
+        assertThat(expected).hasSameElementsAs(solution3.letterCombinations(digits));
     }
 
     @Test
@@ -38,5 +39,6 @@ public void test2() {
         expected = new ArrayList<>(Arrays.asList("ad", "ae", "af", "bd", "be", "bf", "cd", "ce", "cf"));
         assertThat(expected).hasSameElementsAs(solution1.letterCombinations(digits));
         assertThat(expected).hasSameElementsAs(solution2.letterCombinations(digits));
+        assertThat(expected).hasSameElementsAs(solution3.letterCombinations(digits));
     }
 }
