Refactored Letter Case Permutation.java

varunu28 · web-flow · commit d5dda98e3afd · 2021-02-16T06:38:30.000-08:00
diff --git a/Easy/Letter Case Permutation.java b/Easy/Letter Case Permutation.java
@@ -1,29 +1,24 @@
 class Solution {
   public List<String> letterCasePermutation(String S) {
-    Set<String> set = new HashSet<>();
-    helper(S, 0, set, new StringBuilder());
-    return new ArrayList<>(set);
+    List<String> result = new ArrayList<>();
+    helper(S, 0, new StringBuilder(), result);
+    return result;
   }
   
-  private void helper(String s, int idx, Set<String> set, StringBuilder sb) {
+  private void helper(String s, int idx, StringBuilder sb, List<String> result) {
     if (idx == s.length()) {
-      if (sb.length() > 0) {
-        set.add(new StringBuilder(sb.toString()).toString());
-      }
-    }
-    else {
-      char c = s.charAt(idx);
-      if (Character.isDigit(c)) {
-        sb.append(c);
-        helper(s, idx + 1, set, sb);
+      result.add(new String(sb.toString()));
+    } else {
+      if (Character.isDigit(s.charAt(idx))) {
+        sb.append(s.charAt(idx));
+        helper(s, idx + 1, sb, result);
         sb.deleteCharAt(sb.length() - 1);
-      }
-      else {
-        sb.append(Character.toLowerCase(c));
-        helper(s, idx + 1, set, sb);
+      } else {
+        sb.append(Character.toLowerCase(s.charAt(idx)));
+        helper(s, idx + 1, sb, result);
         sb.deleteCharAt(sb.length() - 1);
-        sb.append(Character.toUpperCase(c));
-        helper(s, idx + 1, set, sb);
+        sb.append(Character.toUpperCase(s.charAt(idx)));
+        helper(s, idx + 1, sb, result);
         sb.deleteCharAt(sb.length() - 1);
       }
     }
