So I've made an embarrassingly large number of submissions for this problem. Thing is I submitted in C++ 11 and got WA 1. Afterwards I switched to Visual C++/G++ and got WA 2. Apparently this was caused by asserts that I had left in my program to check if test 1 is actually the example. After I removed them I got Accepted, but still WA 1 in C++11. So my questions would be:

1. Why did it get WA in C++ 11?
2. Why didn't the assert crash the program?

Something happened with the checker, probably. Submittal of a correct solution now results in WA 2.

if k < m return 0 else

amount of 'good' results is equal to С(m), wher C() - Catalanas number
amount of 'bad' results is equal to sum(i = 0.. m, C(i))


for example for m = 3

( - big brother acts
) - smal brothers acts

good results are (independent of k)
((()))
(()())
(())()
()(())
()()()

bad results are
(()) )
()() )
() )
)

now we should calculate C(m) / sum(i = 0.. m, C(i))
C(m) / sum(i = 0.. m, C(i)) = 1 / (sum(i = 0.. m, C(i)) / C(m)) =
= 1 / sum(i = 0.. m, C(i) / C(m)) =
= 1 / sum( i = 0.. m, exp(ln(C(i)) - ln(C(m))) )
We can calculate ln(C(i)) using formula C(i) = F(2 * i) / F(i) / (i + 1), where F(N) = N!

ln(C(i)) = ln(F(2 * i)) - ln(F(i)) - ln(i + 1)
ln(F(i)) = sum(j = 1.. i, ln(j))

now we can calculate sum( i = 0.. m, exp(ln(C(i)) - ln(C(m))) ) accurate to some EPS, and can calculate answer for the task with some EPS.

I tryed to pass this algo, and it doesn't take AC.

Does it wrang algorithm? or it is not enought accurate?

Edited by author 12.03.2009 17:59

Edited by author 17.08.2008 22:54

I don't know whats wrong with it

Program b;

{$APPTYPE CONSOLE}

uses
  SysUtils;

var
  n,k,i,m:integer;
Begin
  readln(n);
  for i:=1 to n do
  begin
    readln(k,m);
    if k=m then
    begin
      writeln(1/(k+1):0:6);
    end
    else
      if m>k then writeln('0')
      else writeln(k/(k+m):0:6);
  end;



End.

Can you tell me the 2nd test

I am new here, so i am not understanding the output format of this problem ( how many digit after the decimal point).
could anyone please tell me about this...........

Edited by author 17.08.2008 16:38

#include <iostream>
using namespace std;
int main()
{
    int n,k,m;
    cin>>n;
    while(n)
    {
        cin>>k>>m;
        if(!k && !m)
            cout<<"1\n";
        else if(k<m)
            cout<<"0\n";
        else
            cout<<(float)k/(k+m)<<endl;
        n--;
    }
    return 0;
}

Edited by author 17.08.2008 15:09

I have got an error --Crash(floating-point invalid operation)-- on the 2nd test.  what does this mean?