C++: Even or Odd


Test whether an integer is even or odd.

There is more than one way to solve this task:

  • Use the even and odd predicates, if the language provides them.
  • Check the least significant digit. With binary integers, i bitwise-and 1 equals 0 iff i is even, or equals 1 iff i is odd.
  • Divide i by 2. The remainder equals 0 iff i is even. The remainder equals +1 or -1 iff i is odd.
  • Use modular congruences:
    • i ≡ 0 (mod 2) iff i is even.
    • i ≡ 1 (mod 2) iff i is odd.

Test using the modulo operator, or use the c example from above.

bool isEven(int x) {
	return x % 2;


Content is available under GNU Free Documentation License 1.2.