Create 367-Valid-Perfect-Square.cpp

cpp/367-Valid-Perfect-Square.cpp

@@ -0,0 +1,25 @@
+/*
+  Given a positive integer num, write a function which returns True if num is a perfect square else False.
+
+  Follow up: Do not use any built-in library function such as sqrt.
+
+  Constraints: 1 <= num <= 2^31 - 1
+
+*/
+
+class Solution {
+public:
+    bool isPerfectSquare(int num) {
+        long long start = 0, end = num;
+        while (start <= end) {
+            long long mid = (start + end) / 2;
+            if (mid * mid == num)
+                return true;
+            else if (mid * mid > num)
+                end = mid - 1;
+            else
+                start = mid + 1;
+        }
+        return false;
+    }
+};