U-Intermediate level of string puzzle OUT(2011-12-17)

[stringpuzzle]

Here I should take the chance to thank Professor IQ Ring(youtube.com/watch?v=gz9aH­GaFGRo), who uploaded his video about the solution to solve this kind of string puzzle, where he called it "Forty Ring-puzzle".

Before his video, I didn't know how to solve it, thanks to his great effort, I come to know the method now.

The following information is for your reference.

Title：Forty Ring-puzzle ( 德致情四十載）Solution

Link：youtube.com/watch?v=gz9aH­GaFGRo