diff --git a/10 October LeetCode Challenge 2021/12_guessNumHighLow.java b/10 October LeetCode Challenge 2021/12_guessNumHighLow.java
new file mode 100644
index 0000000..95e7f28
--- /dev/null
+++ b/10 October LeetCode Challenge 2021/12_guessNumHighLow.java	
@@ -0,0 +1,30 @@
+/* The guess API is defined in the parent class GuessGame.
+   @param num, your guess
+   @return -1 if my number is lower, 1 if my number is higher, otherwise return 0
+      int guess(int num); */
+
+public class Solution extends GuessGame {
+    public int guessNumber(int n) {
+        int low = 1;
+        int high = n;
+        while (low <= high) {
+            int mid1 = low + (high - low) / 3;
+            int mid2 = high - (high - low) / 3;
+            int res1 = guess(mid1);
+            int res2 = guess(mid2);
+            if (res1 == 0)
+                return mid1;
+            if (res2 == 0)
+                return mid2;
+            else if (res1 < 0)
+                high = mid1 - 1;
+            else if (res2 > 0)
+                low = mid2 + 1;
+            else {
+                low = mid1 + 1;
+                high = mid2 - 1;
+            }
+        }
+        return -1;
+    }
+}