[VA] My 2024's very first little teaser

[J-F Garnier]

Here is my solution in 3 BASIC lines and 127 bytes:

20 DESTROY ALL @ OPTION BASE 1 @ DIM U(3),V(3),W(3),M(3,3) @ MAT INPUT U,V,W
40 M(1,2)=W(3) @ M(1,3)=W(2) @ M(2,1)=W(3) @ M(2,3)=W(1) @ M(3,1)=W(2) @ M(3,2)=W(1)
50 MAT V=M*V @ DISP DOT(U,V)

You will notice that there is a '*' sign, but it denotes a matrix multiplication, not an arithmetic operation, so I believe that it is allowed here.

Using the notation

    | a b c |
A = | d e f |
    | g h i |

the code is computing

| 0 i h |   | d |   | ei+fh |
| i 0 g | * | e | = | di+fg |
| h g 0 |   | f |   | dh+eg |

then

| a |   | ei+fh |
| b | . | di+fg | = aei+afh+bdi+bfg+cdh+ceg = per(A)
| c |   | dh+eg |

J-F