Find if x is bigger than y using bitwise operator in C [closed]

问题

This question is unlikely to help any future visitors; it is only relevant to a small geographic area, a specific moment in time, or an extraordinarily narrow situation that is not generally applicable to the worldwide audience of the internet. For help making this question more broadly applicable, visit the help center.

Closed 7 years ago.

If x > y, then this function will return 1, other wise return 0.

so far i have

int isitGreater(int x, int y) {

     return (((y+((~x)+1)) >> 31) & 1);

but it's not working.

Allowed ops: Legal ops: ! ~ & ^ | + << >>

I'm sure I have the logic right, if X - Y and I get a negative number, that means y > x , so therefore the 32nd bit is a 1, so I shift that bit to the right 31 times and then "and" it with "1".

edit: this does not work if x is negative, due to overflow. how can i fix this overflow problem without using conditional statements?

回答1:

Your code works fine for me. Please submit a valid question.

Edit: Your algorithm will not work correctly if x is -2147483648 because -(-2147483648) (or, equivalently, ~(-2147483648)+1) overflows.

回答2:

You can't take the 2's complement of: -2147483648[0x80000000].

来源：https://stackoverflow.com/questions/12524038/find-if-x-is-bigger-than-y-using-bitwise-operator-in-c