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Re:这题也是……比赛时2xxx ms过的……到这就改1000 ms Limit了……TLE…… 那位大大给讲讲算法？

Posted by lake_house at 2008-04-05 00:45:57 on Problem 3219
In Reply To:这题也是……比赛时2xxx ms过的……到这就改1000 ms Limit了……TLE…… 那位大大给讲讲算法？ Posted by:150014 at 2007-05-01 16:45:27 
C(n,k)=C((n-1),k))+C(n-1,k-1)
C(n-1,k) = C(n-2,k)+C(n-2,k-1)
C(n-1,k-1) = C(n-2,k-1)+C(n-2,k-2)
C(n,k)= C(n-2,k)+C(n-2,k-1)*2+C(n-2,k-2) 
=> C(n,k)= (C(n-2,k)+C(n-2,k-2))(mod 2)
..... =>
if k%2==0 C(n,k)= C(n-k,k)+1 (mod 2)
if k%2==1&&n%2==0 C(n,k)= C(n-(k-1),k) (mod 2)
if k%2==1&&n%2==1 C(n,k)= C(n-(k-1),k)+1 (mod 2)
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