About a paradox of post increment operator

[孙宗君]

Hi, all

I am not sure whether this is a proper place to put up with my
question. But I think you can answer my question.

See following two clauses

int x=20, y=35, z;

case 1: x = x++ + y++;
case 2: z = x++ + y++;

in case 1. the result is x = 36;
in case2:  the result is z = 35;

Whether this is a paradox for post increment operator ?

Look forward to your kindly answers.

Thanks very much.

BRs

Zongjun.