Thanks for the solution, very clean and clever.
But this solution seems to have O(n1*n2) time complexity because of remove();
Using HashMap could reduce the complexity to O(max(n1,n2));

Doesn't work if a1 has more values than a2

a1 = [2, 3, 5, 6, 7];
a2 = [4, 25, 9, 36];

null checks are useless, dart is null-safe (a1 and a2 types can't have null value). Without null checks this solution is great

WellDone

Very smart solution. Good job 👍

unreadable crap

I love it!

wow