From 0c3db6842e9b004f16f58c02344a770580e80b18 Mon Sep 17 00:00:00 2001
From: ErdemT09 <erdemturkoglu40@gmail.com>
Date: Wed, 5 May 2021 20:57:19 +0300
Subject: [PATCH] 1087-Solution 1 with TreeSet

---
 .../curated170/medium/BraceExpansion.java     | 41 +++++++++++++++++++
 1 file changed, 41 insertions(+)
 create mode 100644 src/main/java/algorithms/curated170/medium/BraceExpansion.java

diff --git a/src/main/java/algorithms/curated170/medium/BraceExpansion.java b/src/main/java/algorithms/curated170/medium/BraceExpansion.java
new file mode 100644
index 00000000..85b874d7
--- /dev/null
+++ b/src/main/java/algorithms/curated170/medium/BraceExpansion.java
@@ -0,0 +1,41 @@
+package algorithms.curated170.medium;
+
+import java.util.Arrays;
+import java.util.TreeSet;
+
+public class BraceExpansion {
+    public static String[] expand(String S) {
+        TreeSet<String> set = new TreeSet<>();
+        if (S.length() == 0) {
+            return new String[] { "" };
+        } else if (S.length() == 1) {
+            return new String[] { S };
+        }
+
+        if (S.charAt(0) == '{') {
+            int i = 0;
+            while (S.charAt(i) != '}') {
+                i++;
+            }
+            String sub = S.substring(1, i);
+            String[] subs = sub.split(",");
+            String[] strs = expand(S.substring(i + 1)); 
+            for (int j = 0; j < subs.length; j++) {
+                for (String str : strs) {
+                    set.add(subs[j] + str);
+                }
+            }
+        } else {
+            String[] strs = expand(S.substring(1));
+            for (String str : strs) {
+                set.add(S.charAt(0) + str);
+            }
+        }
+        return set.toArray(new String[0]);
+    }
+
+    public static void main(String[] args) {
+        var strs = expand("{a,b}c{d,e}f");
+        System.out.println(Arrays.toString(strs)); //prints [acdf, acef, bcdf, bcef]
+    }
+}