Count the number of 1s in the binary representation of a number?

Short answer: public int CountOnes(int n) { int count = 0; while (n != 0) { n &= (n - 1); // Drops the lowest set bit count++; } return count; } Explanation: Brian Kernighan’s algorithm efficiently removes the lowest set bit each iteration until zero.

Example code

public int CountOnes(int n) {
int count = 0; while (n != 0) { n &= (n - 1); // Drops the lowest set bit count++; }
return count;
} Explanation: Brian Kernighan’s algorithm efficiently removes the lowest set bit each iteration until zero.

Real-world example (ShopNest)

In coding rounds, state complexity aloud, write a clear ShopNest-flavored example (orders, carts), then handle edge cases (empty list, null, overflow).

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.