diff --git a/src/lib.rs b/src/lib.rs
index 00b3c4f..4215b19 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -22,3 +22,4 @@ pub mod p19_remove_nth_node_from_end_of_list;
 pub mod p20_valid_parentheses;
 pub mod p21_merge_two_sorted_lists;
 pub mod p22_generate_parentheses;
+pub mod p23_merge_k_sorted_lists;
diff --git a/src/p22_generate_parentheses.rs b/src/p22_generate_parentheses.rs
index b3e6968..2918f4a 100644
--- a/src/p22_generate_parentheses.rs
+++ b/src/p22_generate_parentheses.rs
@@ -1,9 +1,17 @@
 pub struct Solution;
 impl Solution {
-    // TODO: implement
     pub fn generate_parenthesis(n: i32) -> Vec<String> {
-        
-        return vec![];
+        let mut operations = vec![(0, 0, "".to_string())];
+        let mut result = vec![];
+        while let Some((left, right, s)) = operations.pop() {
+            if s.len() == n as usize * 2 {
+                result.push(s);
+                continue;
+            }
+            if left < n { operations.push((left + 1, right, s.clone() + "(")); }
+            if right < left { operations.push((left, right + 1, s + ")")); }
+        }
+        return result;
     }
 }
 
diff --git a/src/p23_merge_k_sorted_lists.rs b/src/p23_merge_k_sorted_lists.rs
new file mode 100644
index 0000000..9a82e0f
--- /dev/null
+++ b/src/p23_merge_k_sorted_lists.rs
@@ -0,0 +1,27 @@
+use super::linked_list::ListNode;
+
+pub struct Solution;
+impl Solution {
+    // TODO: implement
+    pub fn merge_k_lists(lists: Vec<Option<Box<ListNode>>>) -> Option<Box<ListNode>> {
+        
+        return None;
+    }
+}
+
+#[test]
+fn test1() {
+    assert_eq!(Solution::merge_k_lists(vec![
+        list![1,4,5], list![1,3,4], list![2,6]
+    ]), list![1,1,2,3,4,4,5,6]);
+}
+
+#[test]
+fn test2() {
+    assert_eq!(Solution::merge_k_lists(vec![]), list![]);
+}
+
+#[test]
+fn test3() {
+    assert_eq!(Solution::merge_k_lists(vec![list![]]), list![]);
+}