The integer division there is just taking the floor of the number obtained at the end. 10/3 -> floor(3.33) -> 3 -10/3 -> floor(-3.33) -> -4 (Why it floors) The modulo operation on the other hand is following the mathematical definition.
you are looking for the modulo operator: a % b for example: >>> 26 % 7 5 Of course, maybe they wanted you to implement it yourself, which wouldn’t be too difficult either.
When you have the expression: a % b = c It really means there exists an integer n that makes c as small as possible, but non-negative. a – n*b = c By hand, you can just subtract 2 (or add 2 if your number is negative) over and over until the end result is … Read more
C89, not totally (§3.3.5/6). It can be either -5 or 5, because -5 / 10 can return 0 or -1 (% is defined in terms of a linear equation involving /, * and +): When integers are divided and the division is inexact, if both operands are positive the result of the / operator is … Read more
On x86 (and other processor architectures), integer division and modulo are carried out by a single operation, idiv (div for unsigned values), which produces both quotient and remainder (for word-sized arguments, in AX and DX respectively). This is used in the C library function divmod, which can be optimised by the compiler to a single … Read more
First of all I’d like to note that you cannot even rely on the fact that (-1) % 8 == -1. the only thing you can rely on is that (x / y) * y + ( x % y) == x. However whether or not the remainder is negative is implementation-defined. Reference: C++03 paragraph … Read more
It behaves as it should a % b = a – a / b * b; i.e. it’s the remainder. You can do (a % b + b) % b This expression works as the result of (a % b) is necessarily lower than b, no matter if a is positive or negative. Adding b … Read more
The C++ Standard(2003) says in §5.6/4, […] If the second operand of / or % is zero the behavior is undefined; […] That is, following expressions invoke undefined-behavior(UB): X / 0; //UB X % 0; //UB Note also that -5 % 2 is NOT equal to -(5 % 2) (as Petar seems to suggest in … Read more
Both variants are correct, however in mathematics (number theory in particular), Python’s modulo is most commonly used. In C, you do ((n % M) + M) % M to get the same result as in Python. E. g. ((-1 % 10) + 10) % 10. Note, how it still works for positive integers: ((17 % … Read more