Add Brian Kernighan's algorithm to count set bits by Abhijeet Kundu

Author: abhijeetkundu8

bit_manipulation/count_set_bits.cpp

@@ -0,0 +1,29 @@
+// count_set_bits.cpp
+// Author: Abhijeet Kundu
+// Description: Counts number of set bits (1s) in the binary representation of an integer
+// using Brian Kernighan’s Algorithm.
+// Time Complexity: O(k) where k is number of set bits
+
+#include <iostream>
+#include <cassert>
+
+int countSetBits(int n) {
+    int count = 0;
+    while (n) {
+        n &= (n - 1);  // clears the least significant set bit
+        count++;
+    }
+    return count;
+}
+
+int main() {
+    assert(countSetBits(0) == 0);
+    assert(countSetBits(5) == 2);   // 101 → 2 set bits
+    assert(countSetBits(15) == 4);  // 1111 → 4 set bits
+
+    int n;
+    std::cout << "Enter a number: ";
+    std::cin >> n;
+    std::cout << "Number of set bits: " << countSetBits(n) << "\n";
+    return 0;
+}