Mathematica 24点程序！

cjilyy

f[x1_, s1_, x2_, s2_, x3_, s3_, x4_] :=
Module[{result, i},
5 p  l/ D" c4 V* e  result = {HoldForm[(x1~s1~x2)~s2~(x3~s3~x4)],
  C! N: J" w6 `& p0 L$ M% i0 X* j    HoldForm[x1~s1~(x2~s2~x3~s3~x4)],
2 ?8 h: T) k- ]# J& W5 M( A    HoldForm[x1~s1~x2~s2~(x3~s3~x4)],
! r7 c1 u6 K* N/ K    HoldForm[(x1~s1~x2~s2~x3)~s3~x4],
    HoldForm[x1~s1~(x2~s2~x3)~s3~x4],
7 S" F8 X- b! m0 V6 I. \    HoldForm[(x1~s1~(x2~s2~x3))~s3~x4],
    HoldForm[x1~s1~(x2~s2~(x3~s3~x4))]};
' L( W, M; R- a7 [2 e: X, F) Y  result = Union[result];
  For[i = 1, i <= Length[result], i++,
8 B2 w5 D7 A3 @: G: ^5 R9 U$ g   If[ReleaseHold[result[[i]]] == 24, Print[result[[i]], "=24"];
     (*Print[TreeForm[result[[i]],DirectedEdges->True]]*);];];]

* b) O4 B; P5 E" w' m7 Zfs[x1_, x2_, x3_, x4_] :=
Module[{result, s, sym, num, i, j}, Off[Divide::infy];
  Off[Part::partw];
  Off[Divide::indet];
/ \3 W. O" [6 X& r9 O  s = {Plus, Subtract, Times, Divide};
; x1 ^1 ?, I+ l$ w+ D  sym = Flatten[
    Table[{s[[i]], s[[j]], s[[k]]}, {i, 4}, {j, 4}, {k, 4}], 2];
, |( z" ?' ~; e$ `  sym = Union[sym];
) q( j! y( l1 c/ L% A  num = Permutations[{x1, x2, x3, x4}];
  Do[f[num[[i, 1]], sym[[j, 1]], num[[i, 2]], sym[[j, 2]],
! {3 }+ ~. I, I0 `8 I    num[[i, 3]], sym[[j, 3]], num[[i, 4]]], {i, Length[num]}, {j,
    Length[sym]}]]
4 O0 z" w( X& e
fs[3, 3, 8, 8]