Create prime-number-of-set-bits-in-binary-representation.cpp

Author: kamyu104

C++/prime-number-of-set-bits-in-binary-representation.cpp

@@ -0,0 +1,23 @@
+// Time:  O(log(R - L)) = O(1)
+// Space: O(1)
+
+class Solution {
+public:
+    int countPrimeSetBits(int L, int R) {
+        static const unordered_set<uint32_t> primes{2, 3, 5, 7, 11, 13, 17, 19};
+        int result = 0;
+        for (int i = L; i <= R; ++i) {
+            result += primes.count(bitCount(i));
+        }
+        return result;
+    }
+
+private:
+    int bitCount(uint32_t n) {
+        int count = 0;
+        for (; n; n &= n - 1) {
+            ++count;
+        }
+        return count;
+    }
+};