# Count the number of ways to arrange the balls

There are $12$ different boxes which has number from $1$ to $12$ and $8$ same balls. Ask how many way to arrange these $8$ balls to $12$ boxes such that, the sum of balls in box $1;2;3$ is even number, the sum of balls in box $4;5;6$ is odd number

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Since the number of balls is less than the number of boxes, I like to ask: can we put more than one ball into a singe box? – Hendrik Jan Nov 12 '12 at 13:24

Let's say there are $2k$ balls in boxes $1$ through $3$ and $2l+1$ balls in boxes $4$ through $6$. Then $0\le k\le3$ and $0\le l\le3-k$. In terms of the stars and bars approach, $k$ and $l$ fix the positions of two of the $11$ bars, and it remains to pick positions for $2$ bars among $2k$ stars, $2$ bars among $2l+1$ stars and $5$ bars among $8-2k-(2l+1)$ stars. Thus the total number of ways to arrange the balls is

$$\sum_{k=0}^3\sum_{l=0}^{3-k}\binom{2k+2}2\binom{2l+3}2\binom{12-2(k+l)}5=18864$$

(computation).

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18864.

We can compute this using GAP as follows. We first choose $a$ balls in cells 1..3, then $b$ balls in cells 4..6, then the remainder, $c$, must all go in cells 7..12. For each (a,b,c), we compute the unordered partitions of a,b,c that could go in the cells, 1..3, 4..6 and 7..12, respectively. Then we compute the number of ordered partitions that generate the given unordered partitions.

count:=0;
inc:=0;
for a in Filtered([0..8],i->i mod 2=0) do
for b in Filtered([0..8],i->i mod 2=1) do
c:=8-a-b;
if(c<0) then continue; fi;
Print(a," ball(s) in 1..3;  ",b," ball(s) in 4..6;  ",c," ball(s) elsewhere\n");
for A in RestrictedPartitions(a+3,[1..a+1],3)-1 do
for B in RestrictedPartitions(b+3,[1..b+1],3)-1 do
for C in RestrictedPartitions(c+6,[1..c+1],6)-1 do
orbA:=OrbitLength(SymmetricGroup(3),A,Permuted);
orbB:=OrbitLength(SymmetricGroup(3),B,Permuted);
orbC:=OrbitLength(SymmetricGroup(6),C,Permuted);
inc:=orbA*orbB*orbC;
Print(A," ",B," ",C," ",inc,"\n");
count:=count+inc;
od;
od;
od;
od;
od;
Print("total configurations: ",count,"\n");


Note, the somewhat tricky use of RestrictedPartitions is due to the fact that this function is invalid for parts of size 0.

The output was:

0 ball(s) in 1..3;  1 ball(s) in 4..6;  7 ball(s) elsewhere
[ 0, 0, 0 ] [ 1, 0, 0 ] [ 2, 1, 1, 1, 1, 1 ] 18
[ 0, 0, 0 ] [ 1, 0, 0 ] [ 2, 2, 1, 1, 1, 0 ] 180
[ 0, 0, 0 ] [ 1, 0, 0 ] [ 2, 2, 2, 1, 0, 0 ] 180
[ 0, 0, 0 ] [ 1, 0, 0 ] [ 3, 1, 1, 1, 1, 0 ] 90
[ 0, 0, 0 ] [ 1, 0, 0 ] [ 3, 2, 1, 1, 0, 0 ] 540
[ 0, 0, 0 ] [ 1, 0, 0 ] [ 3, 2, 2, 0, 0, 0 ] 180
[ 0, 0, 0 ] [ 1, 0, 0 ] [ 3, 3, 1, 0, 0, 0 ] 180
[ 0, 0, 0 ] [ 1, 0, 0 ] [ 4, 1, 1, 1, 0, 0 ] 180
[ 0, 0, 0 ] [ 1, 0, 0 ] [ 4, 2, 1, 0, 0, 0 ] 360
[ 0, 0, 0 ] [ 1, 0, 0 ] [ 4, 3, 0, 0, 0, 0 ] 90
[ 0, 0, 0 ] [ 1, 0, 0 ] [ 5, 1, 1, 0, 0, 0 ] 180
[ 0, 0, 0 ] [ 1, 0, 0 ] [ 5, 2, 0, 0, 0, 0 ] 90
[ 0, 0, 0 ] [ 1, 0, 0 ] [ 6, 1, 0, 0, 0, 0 ] 90
[ 0, 0, 0 ] [ 1, 0, 0 ] [ 7, 0, 0, 0, 0, 0 ] 18
0 ball(s) in 1..3;  3 ball(s) in 4..6;  5 ball(s) elsewhere
[ 0, 0, 0 ] [ 1, 1, 1 ] [ 1, 1, 1, 1, 1, 0 ] 6
[ 0, 0, 0 ] [ 1, 1, 1 ] [ 2, 1, 1, 1, 0, 0 ] 60
[ 0, 0, 0 ] [ 1, 1, 1 ] [ 2, 2, 1, 0, 0, 0 ] 60
[ 0, 0, 0 ] [ 1, 1, 1 ] [ 3, 1, 1, 0, 0, 0 ] 60
[ 0, 0, 0 ] [ 1, 1, 1 ] [ 3, 2, 0, 0, 0, 0 ] 30
[ 0, 0, 0 ] [ 1, 1, 1 ] [ 4, 1, 0, 0, 0, 0 ] 30
[ 0, 0, 0 ] [ 1, 1, 1 ] [ 5, 0, 0, 0, 0, 0 ] 6
[ 0, 0, 0 ] [ 2, 1, 0 ] [ 1, 1, 1, 1, 1, 0 ] 36
[ 0, 0, 0 ] [ 2, 1, 0 ] [ 2, 1, 1, 1, 0, 0 ] 360
[ 0, 0, 0 ] [ 2, 1, 0 ] [ 2, 2, 1, 0, 0, 0 ] 360
[ 0, 0, 0 ] [ 2, 1, 0 ] [ 3, 1, 1, 0, 0, 0 ] 360
[ 0, 0, 0 ] [ 2, 1, 0 ] [ 3, 2, 0, 0, 0, 0 ] 180
[ 0, 0, 0 ] [ 2, 1, 0 ] [ 4, 1, 0, 0, 0, 0 ] 180
[ 0, 0, 0 ] [ 2, 1, 0 ] [ 5, 0, 0, 0, 0, 0 ] 36
[ 0, 0, 0 ] [ 3, 0, 0 ] [ 1, 1, 1, 1, 1, 0 ] 18
[ 0, 0, 0 ] [ 3, 0, 0 ] [ 2, 1, 1, 1, 0, 0 ] 180
[ 0, 0, 0 ] [ 3, 0, 0 ] [ 2, 2, 1, 0, 0, 0 ] 180
[ 0, 0, 0 ] [ 3, 0, 0 ] [ 3, 1, 1, 0, 0, 0 ] 180
[ 0, 0, 0 ] [ 3, 0, 0 ] [ 3, 2, 0, 0, 0, 0 ] 90
[ 0, 0, 0 ] [ 3, 0, 0 ] [ 4, 1, 0, 0, 0, 0 ] 90
[ 0, 0, 0 ] [ 3, 0, 0 ] [ 5, 0, 0, 0, 0, 0 ] 18
0 ball(s) in 1..3;  5 ball(s) in 4..6;  3 ball(s) elsewhere
[ 0, 0, 0 ] [ 2, 2, 1 ] [ 1, 1, 1, 0, 0, 0 ] 60
[ 0, 0, 0 ] [ 2, 2, 1 ] [ 2, 1, 0, 0, 0, 0 ] 90
[ 0, 0, 0 ] [ 2, 2, 1 ] [ 3, 0, 0, 0, 0, 0 ] 18
[ 0, 0, 0 ] [ 3, 1, 1 ] [ 1, 1, 1, 0, 0, 0 ] 60
[ 0, 0, 0 ] [ 3, 1, 1 ] [ 2, 1, 0, 0, 0, 0 ] 90
[ 0, 0, 0 ] [ 3, 1, 1 ] [ 3, 0, 0, 0, 0, 0 ] 18
[ 0, 0, 0 ] [ 3, 2, 0 ] [ 1, 1, 1, 0, 0, 0 ] 120
[ 0, 0, 0 ] [ 3, 2, 0 ] [ 2, 1, 0, 0, 0, 0 ] 180
[ 0, 0, 0 ] [ 3, 2, 0 ] [ 3, 0, 0, 0, 0, 0 ] 36
[ 0, 0, 0 ] [ 4, 1, 0 ] [ 1, 1, 1, 0, 0, 0 ] 120
[ 0, 0, 0 ] [ 4, 1, 0 ] [ 2, 1, 0, 0, 0, 0 ] 180
[ 0, 0, 0 ] [ 4, 1, 0 ] [ 3, 0, 0, 0, 0, 0 ] 36
[ 0, 0, 0 ] [ 5, 0, 0 ] [ 1, 1, 1, 0, 0, 0 ] 60
[ 0, 0, 0 ] [ 5, 0, 0 ] [ 2, 1, 0, 0, 0, 0 ] 90
[ 0, 0, 0 ] [ 5, 0, 0 ] [ 3, 0, 0, 0, 0, 0 ] 18
0 ball(s) in 1..3;  7 ball(s) in 4..6;  1 ball(s) elsewhere
[ 0, 0, 0 ] [ 3, 2, 2 ] [ 1, 0, 0, 0, 0, 0 ] 18
[ 0, 0, 0 ] [ 3, 3, 1 ] [ 1, 0, 0, 0, 0, 0 ] 18
[ 0, 0, 0 ] [ 4, 2, 1 ] [ 1, 0, 0, 0, 0, 0 ] 36
[ 0, 0, 0 ] [ 4, 3, 0 ] [ 1, 0, 0, 0, 0, 0 ] 36
[ 0, 0, 0 ] [ 5, 1, 1 ] [ 1, 0, 0, 0, 0, 0 ] 18
[ 0, 0, 0 ] [ 5, 2, 0 ] [ 1, 0, 0, 0, 0, 0 ] 36
[ 0, 0, 0 ] [ 6, 1, 0 ] [ 1, 0, 0, 0, 0, 0 ] 36
[ 0, 0, 0 ] [ 7, 0, 0 ] [ 1, 0, 0, 0, 0, 0 ] 18
2 ball(s) in 1..3;  1 ball(s) in 4..6;  5 ball(s) elsewhere
[ 1, 1, 0 ] [ 1, 0, 0 ] [ 1, 1, 1, 1, 1, 0 ] 54
[ 1, 1, 0 ] [ 1, 0, 0 ] [ 2, 1, 1, 1, 0, 0 ] 540
[ 1, 1, 0 ] [ 1, 0, 0 ] [ 2, 2, 1, 0, 0, 0 ] 540
[ 1, 1, 0 ] [ 1, 0, 0 ] [ 3, 1, 1, 0, 0, 0 ] 540
[ 1, 1, 0 ] [ 1, 0, 0 ] [ 3, 2, 0, 0, 0, 0 ] 270
[ 1, 1, 0 ] [ 1, 0, 0 ] [ 4, 1, 0, 0, 0, 0 ] 270
[ 1, 1, 0 ] [ 1, 0, 0 ] [ 5, 0, 0, 0, 0, 0 ] 54
[ 2, 0, 0 ] [ 1, 0, 0 ] [ 1, 1, 1, 1, 1, 0 ] 54
[ 2, 0, 0 ] [ 1, 0, 0 ] [ 2, 1, 1, 1, 0, 0 ] 540
[ 2, 0, 0 ] [ 1, 0, 0 ] [ 2, 2, 1, 0, 0, 0 ] 540
[ 2, 0, 0 ] [ 1, 0, 0 ] [ 3, 1, 1, 0, 0, 0 ] 540
[ 2, 0, 0 ] [ 1, 0, 0 ] [ 3, 2, 0, 0, 0, 0 ] 270
[ 2, 0, 0 ] [ 1, 0, 0 ] [ 4, 1, 0, 0, 0, 0 ] 270
[ 2, 0, 0 ] [ 1, 0, 0 ] [ 5, 0, 0, 0, 0, 0 ] 54
2 ball(s) in 1..3;  3 ball(s) in 4..6;  3 ball(s) elsewhere
[ 1, 1, 0 ] [ 1, 1, 1 ] [ 1, 1, 1, 0, 0, 0 ] 60
[ 1, 1, 0 ] [ 1, 1, 1 ] [ 2, 1, 0, 0, 0, 0 ] 90
[ 1, 1, 0 ] [ 1, 1, 1 ] [ 3, 0, 0, 0, 0, 0 ] 18
[ 1, 1, 0 ] [ 2, 1, 0 ] [ 1, 1, 1, 0, 0, 0 ] 360
[ 1, 1, 0 ] [ 2, 1, 0 ] [ 2, 1, 0, 0, 0, 0 ] 540
[ 1, 1, 0 ] [ 2, 1, 0 ] [ 3, 0, 0, 0, 0, 0 ] 108
[ 1, 1, 0 ] [ 3, 0, 0 ] [ 1, 1, 1, 0, 0, 0 ] 180
[ 1, 1, 0 ] [ 3, 0, 0 ] [ 2, 1, 0, 0, 0, 0 ] 270
[ 1, 1, 0 ] [ 3, 0, 0 ] [ 3, 0, 0, 0, 0, 0 ] 54
[ 2, 0, 0 ] [ 1, 1, 1 ] [ 1, 1, 1, 0, 0, 0 ] 60
[ 2, 0, 0 ] [ 1, 1, 1 ] [ 2, 1, 0, 0, 0, 0 ] 90
[ 2, 0, 0 ] [ 1, 1, 1 ] [ 3, 0, 0, 0, 0, 0 ] 18
[ 2, 0, 0 ] [ 2, 1, 0 ] [ 1, 1, 1, 0, 0, 0 ] 360
[ 2, 0, 0 ] [ 2, 1, 0 ] [ 2, 1, 0, 0, 0, 0 ] 540
[ 2, 0, 0 ] [ 2, 1, 0 ] [ 3, 0, 0, 0, 0, 0 ] 108
[ 2, 0, 0 ] [ 3, 0, 0 ] [ 1, 1, 1, 0, 0, 0 ] 180
[ 2, 0, 0 ] [ 3, 0, 0 ] [ 2, 1, 0, 0, 0, 0 ] 270
[ 2, 0, 0 ] [ 3, 0, 0 ] [ 3, 0, 0, 0, 0, 0 ] 54
2 ball(s) in 1..3;  5 ball(s) in 4..6;  1 ball(s) elsewhere
[ 1, 1, 0 ] [ 2, 2, 1 ] [ 1, 0, 0, 0, 0, 0 ] 54
[ 1, 1, 0 ] [ 3, 1, 1 ] [ 1, 0, 0, 0, 0, 0 ] 54
[ 1, 1, 0 ] [ 3, 2, 0 ] [ 1, 0, 0, 0, 0, 0 ] 108
[ 1, 1, 0 ] [ 4, 1, 0 ] [ 1, 0, 0, 0, 0, 0 ] 108
[ 1, 1, 0 ] [ 5, 0, 0 ] [ 1, 0, 0, 0, 0, 0 ] 54
[ 2, 0, 0 ] [ 2, 2, 1 ] [ 1, 0, 0, 0, 0, 0 ] 54
[ 2, 0, 0 ] [ 3, 1, 1 ] [ 1, 0, 0, 0, 0, 0 ] 54
[ 2, 0, 0 ] [ 3, 2, 0 ] [ 1, 0, 0, 0, 0, 0 ] 108
[ 2, 0, 0 ] [ 4, 1, 0 ] [ 1, 0, 0, 0, 0, 0 ] 108
[ 2, 0, 0 ] [ 5, 0, 0 ] [ 1, 0, 0, 0, 0, 0 ] 54
4 ball(s) in 1..3;  1 ball(s) in 4..6;  3 ball(s) elsewhere
[ 2, 1, 1 ] [ 1, 0, 0 ] [ 1, 1, 1, 0, 0, 0 ] 180
[ 2, 1, 1 ] [ 1, 0, 0 ] [ 2, 1, 0, 0, 0, 0 ] 270
[ 2, 1, 1 ] [ 1, 0, 0 ] [ 3, 0, 0, 0, 0, 0 ] 54
[ 2, 2, 0 ] [ 1, 0, 0 ] [ 1, 1, 1, 0, 0, 0 ] 180
[ 2, 2, 0 ] [ 1, 0, 0 ] [ 2, 1, 0, 0, 0, 0 ] 270
[ 2, 2, 0 ] [ 1, 0, 0 ] [ 3, 0, 0, 0, 0, 0 ] 54
[ 3, 1, 0 ] [ 1, 0, 0 ] [ 1, 1, 1, 0, 0, 0 ] 360
[ 3, 1, 0 ] [ 1, 0, 0 ] [ 2, 1, 0, 0, 0, 0 ] 540
[ 3, 1, 0 ] [ 1, 0, 0 ] [ 3, 0, 0, 0, 0, 0 ] 108
[ 4, 0, 0 ] [ 1, 0, 0 ] [ 1, 1, 1, 0, 0, 0 ] 180
[ 4, 0, 0 ] [ 1, 0, 0 ] [ 2, 1, 0, 0, 0, 0 ] 270
[ 4, 0, 0 ] [ 1, 0, 0 ] [ 3, 0, 0, 0, 0, 0 ] 54
4 ball(s) in 1..3;  3 ball(s) in 4..6;  1 ball(s) elsewhere
[ 2, 1, 1 ] [ 1, 1, 1 ] [ 1, 0, 0, 0, 0, 0 ] 18
[ 2, 1, 1 ] [ 2, 1, 0 ] [ 1, 0, 0, 0, 0, 0 ] 108
[ 2, 1, 1 ] [ 3, 0, 0 ] [ 1, 0, 0, 0, 0, 0 ] 54
[ 2, 2, 0 ] [ 1, 1, 1 ] [ 1, 0, 0, 0, 0, 0 ] 18
[ 2, 2, 0 ] [ 2, 1, 0 ] [ 1, 0, 0, 0, 0, 0 ] 108
[ 2, 2, 0 ] [ 3, 0, 0 ] [ 1, 0, 0, 0, 0, 0 ] 54
[ 3, 1, 0 ] [ 1, 1, 1 ] [ 1, 0, 0, 0, 0, 0 ] 36
[ 3, 1, 0 ] [ 2, 1, 0 ] [ 1, 0, 0, 0, 0, 0 ] 216
[ 3, 1, 0 ] [ 3, 0, 0 ] [ 1, 0, 0, 0, 0, 0 ] 108
[ 4, 0, 0 ] [ 1, 1, 1 ] [ 1, 0, 0, 0, 0, 0 ] 18
[ 4, 0, 0 ] [ 2, 1, 0 ] [ 1, 0, 0, 0, 0, 0 ] 108
[ 4, 0, 0 ] [ 3, 0, 0 ] [ 1, 0, 0, 0, 0, 0 ] 54
6 ball(s) in 1..3;  1 ball(s) in 4..6;  1 ball(s) elsewhere
[ 2, 2, 2 ] [ 1, 0, 0 ] [ 1, 0, 0, 0, 0, 0 ] 18
[ 3, 2, 1 ] [ 1, 0, 0 ] [ 1, 0, 0, 0, 0, 0 ] 108
[ 3, 3, 0 ] [ 1, 0, 0 ] [ 1, 0, 0, 0, 0, 0 ] 54
[ 4, 1, 1 ] [ 1, 0, 0 ] [ 1, 0, 0, 0, 0, 0 ] 54
[ 4, 2, 0 ] [ 1, 0, 0 ] [ 1, 0, 0, 0, 0, 0 ] 108
[ 5, 1, 0 ] [ 1, 0, 0 ] [ 1, 0, 0, 0, 0, 0 ] 108
[ 6, 0, 0 ] [ 1, 0, 0 ] [ 1, 0, 0, 0, 0, 0 ] 54
total configurations: 18864

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I agree that there's probably no particularly clever way to find this number that doesn't involve adding up the various possibilities for the even and odd numbers of balls in the groups of boxes, but we can do with a bit less computational effort than this; see my answer. – joriki Nov 12 '12 at 13:50
Ah yes, I should have used the stars and bars approach; I snipped the comment from my answer. – Douglas S. Stones Nov 12 '12 at 20:52