Have you tried limiting the memory on the java process? On the "JVM arguements" on the external language server settings add a parameter like "-Xmx16g" to limit the memory to 16gb. Have a google for "JVM arguments xmx" there are loads of setting for memory to play with. 

a-z only is too hard using my method, so I have switched over to same as as you guys. Up to 73 now:

 f i=0:1:25,32:1:57{s m=$tr(m,$c(i+65),i#2)} q $re($e(m,1,*-1))_$e(m,*)

Stuart, your program above fails some of the tests: 1s an 0s round the wrong way.

Here is my effort:

f i=$l(M),1:1:i-1{s c=$e(M,i),b=$s(c?1A:$a(c)-1#2,1:c)_$g(b)} q b