Add 22_Generate_Parentheses.java

Author: Sean Prashad

Backtracking/22_Generate_Parentheses.java

@@ -0,0 +1,30 @@
+class Solution {
+ public List<String> generateParenthesis(int n) {
+ if (n <= 0) {
+ return Collections.emptyList();
+ }
+
+ List<String> result = new ArrayList<>();
+ dfs(n, 0, 0, new StringBuilder(), result);
+ return result;
+ }
+
+ private void dfs(int n, int open, int close, StringBuilder sb, List<String> result) {
+ if (open == n && close == n) {
+ result.add(sb.toString());
+ return;
+ }
+
+ if (open < n) {
+ sb.append('(');
+ dfs(n, open + 1, close, sb, result);
+ sb.deleteCharAt(sb.length() - 1);
+ }
+
+ if (close < open) {
+ sb.append(')');
+ dfs(n, open, close + 1, sb, result);
+ sb.deleteCharAt(sb.length() - 1);
+ }
+ }
+}