diff --git a/DAY15/CheckStringPalindrome.cs b/DAY15/CheckStringPalindrome.cs
new file mode 100644
index 0000000..931c03f
--- /dev/null
+++ b/DAY15/CheckStringPalindrome.cs
@@ -0,0 +1,12 @@
+public class Solution {
+    public bool IsPalindrome(int x) {
+        	
+			var s = x.ToString();
+			    
+      char[] charArray = s.ToCharArray();
+      Array.Reverse( charArray );
+      var sresult = new string( charArray );
+			
+			return sresult == s;
+    }
+}
diff --git a/DAY36/MaskPassword.cs b/DAY36/MaskPassword.cs
new file mode 100644
index 0000000..1d4f3ef
--- /dev/null
+++ b/DAY36/MaskPassword.cs
@@ -0,0 +1,10 @@
+public string MaskStringCreate()
+{
+    string myAwesomePassword = "Password12345!"; //Pas*********
+
+    return string.Create(myAwesomePassword.Length, myAwesomePassword, (span, value) =>
+    {
+        value.AsSpan().CopyTo(span);
+        span[3..].Fill('*');
+    });
+}
diff --git a/DAY37/RotatedSortedArray.cs b/DAY37/RotatedSortedArray.cs
new file mode 100644
index 0000000..bdb50b7
--- /dev/null
+++ b/DAY37/RotatedSortedArray.cs
@@ -0,0 +1,38 @@
+public class Solution {
+    public int Search(int[] nums, int target) {
+        for (var i = 0; i < nums.Length; i++)
+        {
+            if (nums[i] == target)
+            {
+                return i;
+            }
+        }
+        return -1;
+    }
+}
+
+
+/*
+There is an integer array nums sorted in ascending order (with distinct values).
+
+Prior to being passed to your function, nums is possibly rotated at an unknown pivot index k (1 <= k < nums.length) such that the resulting array is [nums[k], nums[k+1], ..., nums[n-1], nums[0], nums[1], ..., nums[k-1]] (0-indexed). For example, [0,1,2,4,5,6,7] might be rotated at pivot index 3 and become [4,5,6,7,0,1,2].
+
+Given the array nums after the possible rotation and an integer target, return the index of target if it is in nums, or -1 if it is not in nums.
+
+You must write an algorithm with O(log n) runtime complexity.
+
+ 
+
+Example 1:
+
+Input: nums = [4,5,6,7,0,1,2], target = 0
+Output: 4
+Example 2:
+
+Input: nums = [4,5,6,7,0,1,2], target = 3
+Output: -1
+Example 3:
+
+Input: nums = [1], target = 0
+Output: -1
+*/