Method pop

225-implement-stack-using-queues.rs:16–21

(&mut self)

    }

    fn pop(&mut self) -> i32 {
        let index = self.stack_box.len()-1;
        let ret = self.stack_box[index];
        self.stack_box.remove(index);
        ret
    }

    fn top(&self) -> i32 {
        *self.stack_box.last().unwrap()