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Spark和SQL弱爆了, 看我NB的Mathematica新手的做法,三行代码搞定,而且快 
In[1]:= F[n_] := If[n < 10, n + 1, 9 - (n - 9) + 1] - Mod[(n + 1), 2];
S = Select[Tuples[Range[0, 9], 2], #[[1]] != #[[2]] &];
Total[Map[F, Total[S, {2}]]]/(10*9)^2
Out[3]= 29/405
In[4]:= F[n_] := If[n < 110, (n - 10) - 10 + 1, 99 - (n - 99) + 1] - Mod[(n + 1), 2];
S = Select[Tuples[Range[10, 99], 2], #[[1]] != #[[2]] &];
Total[Map[F, Total[S, {2}]]]/(90*89)^2
Out[6]= 7967/1069335 |
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