when trying to update from (ux,uy) to (vx,vy)  i was checking if (vx,vy) was already popped from priority_queue.

this got me wa 22 many times. later, just out of frustation i removed the check and let (vx,vy) be updated even after it was once popped. and u know what, mysteriously got AC. of course, there has to be some logical explanation behind that.

please explain anyone?

Thanks in advance.

I followed by your advice, and also suprised!