Question 17
Every cell of a $4\times4$ table contains a playing card (their suits are shown in the picture). One lead allows switching the positions of any two cards. At least, how many leads will be played so that each row and each column will contain all suits?
Editable table:
| Column 1 | Column 2 | Column 3 | Column 4 |
| --- | --- | --- | --- |
| ♥ | ♥ | ♦ | ♣ |
| ♦ | ♠ | ♠ | ♥ |
| ♣ | ♦ | ♠ | ♣ |
| ♠ | ♣ | ♥ | ♦ |
♥ hearts; ♦ diamonds; ♣ clubs; ♠ spades.
Editable table:
| Column 1 | Column 2 | Column 3 | Column 4 |
| --- | --- | --- | --- |
| ♥ | ♥ | ♦ | ♣ |
| ♦ | ♠ | ♠ | ♥ |
| ♣ | ♦ | ♠ | ♣ |
| ♠ | ♣ | ♥ | ♦ |
♥ hearts; ♦ diamonds; ♣ clubs; ♠ spades.