Generated Parenthesis in Java

Author: fs788

GenerateParentheses.java

@@ -0,0 +1,25 @@
+class Solution {
+    public List<String> generateParenthesis(int n) {
+        List<String> ans = new ArrayList();
+        backtrack(ans, new StringBuilder(), 0, 0, n);
+        return ans;
+    }
+
+    public void backtrack(List<String> ans, StringBuilder cur, int open, int close, int max){
+        if (cur.length() == max * 2) {
+            ans.add(cur.toString());
+            return;
+        }
+
+        if (open < max) {
+            cur.append("(");
+            backtrack(ans, cur, open+1, close, max);
+            cur.deleteCharAt(cur.length() - 1);
+        }
+        if (close < open) {
+            cur.append(")");
+            backtrack(ans, cur, open, close+1, max);
+            cur.deleteCharAt(cur.length() - 1);
+        }
+    }
+}