Boolean expression with integer increments gives unexpected results

Question

    #include <stdio.h>

    int main()

    {

       int x, y, z; 

       x=y=z=1; 

       z = ++x || ++y && ++z; 

       printf("%d, %d, %d", x, y,z);

       return 0;

    }

I am getting output 2, 1, 1. I need and explanation why Y is 1 in output?

Answer 1

The logical operation || is so-called "short-circuit" or "lazy" operation. If the left operand of such an operator is evaluating to logical true or a non-zero, the right operand won't be evaluated.

So in your case:

z = ++x || ++y && ++z;

++x is evaluating to 2, making x equal 2. This is non-zero, so everything on the right side is not evaluated, so y and z are not incremented. And z is assigned by the result of the logical OR operation, i.e. 1. And this is what you see.

Boolean expression with integer increments gives unexpected results

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