diff --git a/guess-number-higher-or-lower/sol.rs b/guess-number-higher-or-lower/sol.rs
new file mode 100644
index 0000000..fc97328
--- /dev/null
+++ b/guess-number-higher-or-lower/sol.rs
@@ -0,0 +1,22 @@
+/** 
+ * Forward declaration of guess API.
+ * @param  num   your guess
+ * @return 	     -1 if num is higher than the picked number
+ *			      1 if num is lower than the picked number
+ *               otherwise return 0
+ * unsafe fn guess(num: i32) -> i32 {}
+ */
+impl Solution {
+    unsafe fn guessNumber(n: i32) -> i32 {
+        let (mut min, mut max) = (1, n);
+        while min != max {
+            let guess_num = max / 2 + min / 2;
+            match guess(guess_num) {
+                -1 => max = guess_num - 1,
+                1 => min = guess_num + 1,
+                _ => return guess_num
+            }
+        }
+        min
+    }
+}
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