TAOCP 7.2.2.1 Exercise 401
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Section 7.2.2.1: Dancing Links
Exercise 401. [22] [22] Find all $4 \times 4$ kenken puzzles whose unique solution is the latin square shown at the right, and whose clues belong to two cells. Furthermore, there should be exactly two cages for each of the four operations $+, -, \times, \div$.
$$\begin{matrix} 1 & 2 & 3 & 4 \ 2 & 1 & 4 & 3 \ 4 & 3 & 1 & 2 \ 3 & 4 & 2 & 1 \end{matrix}$$
Verified: no
Solve time: 4m31s
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