Create guess-number-higher-or-lower.cpp

Author: kamyu104

C++/guess-number-higher-or-lower.cpp

@@ -0,0 +1,23 @@
+// Time:  O(logn)
+// Space: O(1)
+
+// Forward declaration of guess API.
+// @param num, your guess
+// @return -1 if my number is lower, 1 if my number is higher, otherwise return 0
+int guess(int num);
+
+class Solution {
+public:
+    int guessNumber(int n) {
+        int left = 1, right = n;
+        while (left <= right) {
+            const auto mid = left + (right - left) / 2;
+            if (guess(mid) <= 0) {
+                right = mid - 1;
+            } else {
+                left = mid + 1;
+            }
+        }
+        return left;
+    }
+};