You can use the following methods to see the results of each step.
a
=LET(
r,A61:Z88,
a,INDEX(A:ZZ,MIN(IF(r<>"",ROW(r))),MIN(IF(r<>"",COLUMN(r)))):INDEX(A:ZZ,MAX(IF(r<>"",ROW(r))),MAX(IF(r<>"",COLUMN(r)))),
b,DROP(REDUCE("",SEQUENCE(ROWS(a)),LAMBDA(x,y,VSTACK(x,IF(ISODD(y),INDEX(a,y,),SCAN(,INDEX(a,y,),LAMBDA(m,n,IF(n=0,m,n))))))),1),
c,DROP(REDUCE("",SEQUENCE(ROWS(b)-2),LAMBDA(x,y,IF(ISODD(y),x,VSTACK(x,DROP(REDUCE("",SEQUENCE(COLUMNS(b)),LAMBDA(m,n,IF(INDEX(b,y+1,n)<>0,VSTACK(m,INDEX(b,y,n),INDEX(b,y+2,n)),m))),1))))),1),
d,WRAPROWS(c,2),
a
)
b
=LET(
r,A61:Z88,
a,INDEX(A:ZZ,MIN(IF(r<>"",ROW(r))),MIN(IF(r<>"",COLUMN(r)))):INDEX(A:ZZ,MAX(IF(r<>"",ROW(r))),MAX(IF(r<>"",COLUMN(r)))),
b,DROP(REDUCE("",SEQUENCE(ROWS(a)),LAMBDA(x,y,VSTACK(x,IF(ISODD(y),INDEX(a,y,),SCAN(,INDEX(a,y,),LAMBDA(m,n,IF(n=0,m,n))))))),1),
c,DROP(REDUCE("",SEQUENCE(ROWS(b)-2),LAMBDA(x,y,IF(ISODD(y),x,VSTACK(x,DROP(REDUCE("",SEQUENCE(COLUMNS(b)),LAMBDA(m,n,IF(INDEX(b,y+1,n)<>0,VSTACK(m,INDEX(b,y,n),INDEX(b,y+2,n)),m))),1))))),1),
d,WRAPROWS(c,2),
b
)
c
=LET(
r,A61:Z88,
a,INDEX(A:ZZ,MIN(IF(r<>"",ROW(r))),MIN(IF(r<>"",COLUMN(r)))):INDEX(A:ZZ,MAX(IF(r<>"",ROW(r))),MAX(IF(r<>"",COLUMN(r)))),
b,DROP(REDUCE("",SEQUENCE(ROWS(a)),LAMBDA(x,y,VSTACK(x,IF(ISODD(y),INDEX(a,y,),SCAN(,INDEX(a,y,),LAMBDA(m,n,IF(n=0,m,n))))))),1),
c,DROP(REDUCE("",SEQUENCE(ROWS(b)-2),LAMBDA(x,y,IF(ISODD(y),x,VSTACK(x,DROP(REDUCE("",SEQUENCE(COLUMNS(b)),LAMBDA(m,n,IF(INDEX(b,y+1,n)<>0,VSTACK(m,INDEX(b,y,n),INDEX(b,y+2,n)),m))),1))))),1),
d,WRAPROWS(c,2),
c
)
d
=LET(
r,A61:Z88,
a,INDEX(A:ZZ,MIN(IF(r<>"",ROW(r))),MIN(IF(r<>"",COLUMN(r)))):INDEX(A:ZZ,MAX(IF(r<>"",ROW(r))),MAX(IF(r<>"",COLUMN(r)))),
b,DROP(REDUCE("",SEQUENCE(ROWS(a)),LAMBDA(x,y,VSTACK(x,IF(ISODD(y),INDEX(a,y,),SCAN(,INDEX(a,y,),LAMBDA(m,n,IF(n=0,m,n))))))),1),
c,DROP(REDUCE("",SEQUENCE(ROWS(b)-2),LAMBDA(x,y,IF(ISODD(y),x,VSTACK(x,DROP(REDUCE("",SEQUENCE(COLUMNS(b)),LAMBDA(m,n,IF(INDEX(b,y+1,n)<>0,VSTACK(m,INDEX(b,y,n),INDEX(b,y+2,n)),m))),1))))),1),
d,WRAPROWS(c,2),
d
)
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