diff --git a/find-minimum-in-rotated-sorted-array/s0ooo0k.java b/find-minimum-in-rotated-sorted-array/s0ooo0k.java
new file mode 100644
index 000000000..646cc8128
--- /dev/null
+++ b/find-minimum-in-rotated-sorted-array/s0ooo0k.java
@@ -0,0 +1,19 @@
+class Solution {
+    /*
+     * 시간복잡도 O(log n)
+     */
+    public int findMin(int[] nums) {
+        int left = 0;
+        int right = nums.length-1;
+
+        while(left<right) {
+            int mid =(right - left)/2+left;
+            if(nums[right]<nums[mid]) {
+                left=mid+1;
+            }
+            else right=mid;
+        }
+        return nums[left];
+    }
+}
+
diff --git a/maximum-depth-of-binary-tree/s0ooo0k.java b/maximum-depth-of-binary-tree/s0ooo0k.java
new file mode 100644
index 000000000..22c563c26
--- /dev/null
+++ b/maximum-depth-of-binary-tree/s0ooo0k.java
@@ -0,0 +1,10 @@
+class Solution {
+    /*
+     * 시간복잡도: O(n)
+     */
+    public int maxDepth(TreeNode root) {
+        if(root==null) return 0;
+        return 1+Math.max(maxDepth(root.left), maxDepth(root.right));
+    }
+}
+
diff --git a/merge-two-sorted-lists/s0ooo0k.java b/merge-two-sorted-lists/s0ooo0k.java
new file mode 100644
index 000000000..a3e07fec0
--- /dev/null
+++ b/merge-two-sorted-lists/s0ooo0k.java
@@ -0,0 +1,19 @@
+class Solution {
+    /*
+     * 시간복잡도 O(m+n) m: list1의 길이, n: list2의 길이
+     */
+    public ListNode mergeTwoLists(ListNode list1, ListNode list2) {
+        if(list1==null) return list2;
+        if(list2==null) return list1;
+
+        if(list1.val <= list2.val) {
+            list1.next = mergeTwoLists(list1.next, list2);
+            return list1;
+        }
+        else {/*  */
+            list2.next = mergeTwoLists(list1, list2.next);
+            return list2;
+        }
+    }
+}
+