231. Power of Two

231. Power of Two.cpp

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+// ---------------- Approach ----------------
+//
+// - A number n is a power of two if:
+//     - n > 0
+//     - In binary representation, it has exactly one set bit.
+//
+// - Trick: For powers of two, `n & (n - 1)` = 0
+//   Example: n = 8 (1000), n-1 = 7 (0111), AND = 0000
+//
+// - This works because subtracting 1 flips all bits after the rightmost set bit.
+// - If n has more than one set bit, the result won’t be zero.
+
+
+// ---------------- Intuition ----------------
+//
+// Binary representation of powers of two looks like:
+//   1 (0001), 2 (0010), 4 (0100), 8 (1000), 16 (10000) ...
+// Only one bit is set to 1.
+//
+// Thus, checking `(n > 0) && (n & (n - 1)) == 0` is the most efficient way.
+
+
+// ---------------- Solution in Code ----------------
+
+class Solution {
+public:
+    bool isPowerOfTwo(int n) {
+        if (n <= 0) return false;
+        return (n & (n - 1)) == 0;
+    }
+};