The array below represents a set of 16 playing cards, with the A's representing Aces:

 A  5  5  A
 5  2  4 10
 3  8  7  4
 A  A  2  6

Divide the array into sections of adjacent cards so that the sum of the cards' values in each section will be 21. Each Ace can represent either 1 or 11 and you must determine how many sections are needed.

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From Page-a-Day Calendar 2016: Amazing Mind Benders, by Puzzability (Mike Shenk, Amy Goldstein and Robert Leighton), Workman Publishing, NY; puzzle for August 6,7.

(In reply to Full solution - SPOILER by Ady TZIDON)

I assume the special characters were to tie together members of a group.  I should have mentioned, I guess, that meeting at a corner doesn't make the cards adjacent: they must share a common side. In your * group, the 2 and 3 meet at only a corner.

Posted by Charlie on 2016-08-11 09:06:28