@StefanPochmann Yes, it's somehow embarrassed, I used to write my code in a way without copy-like assignment but it's sloppy since I have to operate pointers by point.next.next.next. You're right and I have modified my code for concision and consistency. Besides I have made some animation and images for explaination, but it's pitty I can't show them here.
Thanks you very much for your kind comments and patience.
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