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## Discussion of Problem 1402. Cocktails

WA20
Posted by Dmitrij 8 May 2012 00:21
Can anyone explain me, why this code got WA20:
program Project1;

{\$APPTYPE CONSOLE}

uses
SysUtils;

var
f : array[1..21] of extended;
d, c : array[-1..21, -1..21] of extended;
res : extended;
i, j, k, n : integer;

begin

res := 0;
f[1] := 1;
for i := 2 to n do
f[i] := f[i - 1] * i;
c[0][0] := 1;
for i := 1 to n do
for j := 0 to i do
c[i][j] := c[i - 1][j] + c[i - 1][j - 1];
for i := 2 to n do
res := res + c[n][i] * f[i];

writeln(res:0:0);

end.

But this code got AC:
program Project2;

{\$APPTYPE CONSOLE}

uses
SysUtils;

var
n : integer;
s : array[1..21] of string;

begin

s[1] := '0';
s[2] := '2';
s[3] := '12';
s[4] := '60';
s[5] := '320';
s[6] := '1950';
s[7] := '13692';
s[8] := '109592';
s[9] := '986400';
s[10] := '9864090';
s[11] := '108505100';
s[12] := '1302061332';
s[13] := '16926797472';
s[14] := '236975164790';
s[15] := '3554627472060';
s[16] := '56874039553200';
s[17] := '966858672404672';
s[18] := '17403456103284402';
s[19] := '330665665962403980';
s[20] := '6613313319248079980';
s[21] := '138879579704209680000';

writeln(s[n]);

end.

In spite of the fact, that answers for second programm I took as the results of the first program :)

Edited by author 08.05.2012 00:24
Re: WA20
Posted by Andrew Sboev 8 May 2012 23:38
Simple school maths. Just one formula from combinatorics. Without any precalc.

Edited by author 08.05.2012 23:38
Re: WA20
Posted by Dmitrij 13 May 2012 11:53
This is not my question.I couldn't understend why writeln(res:0:0) got WA, but on all my tests it's OK.Now I think it's becouse of old version of compiler here.