卷积与多项式乘法与FFT

背景zjoi2014力

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E [ j ] = F [ j ] / q [ j ] E[j]=F[j]/q[j] E[j]=F[j]/q[j]

卷积与多项式乘法

A ( x ) = a 0 + a 1 x + a 2 x 2 + . . . + a n − 1 x n − 1 B ( x ) = b 0 + b 1 x + b 2 x 2 + . . . + b n − 1 x n − 1 C ( x ) = a 0 b 0 + ( a 0 b 1 + a 1 b 0 ) x + . . . + ( a n − 1 b n − 1 ) x n − 2 ∴ c n = a 0 b n + a 1 b n − 1 + . . . = ∑ i = 0 n a i b n − i A(x)=a_0+a_1x+a_2x^2+...+a_{n-1}x^{n-1}\\ B(x)=b_0+b_1x+b_2x^2+...+b_{n-1}x^{n-1}\\ C(x)=a_0b_0+(a_0b_1+a_1b_0)x+...+(a_{n-1}b_{n-1})x^{n-2}\\ ∴c_n=a_0b_n+a_1b_{n-1}+...=\sum_{i=0}^{n}a_ib_{n-i}\\ A(x)=a0+a1x+a2x2+...+an1xn1B(x)=b0+b1x+b2x2+...+bn1xn1C(x)=a0b0+(a0b1+a1b0)x+...+(an1bn1)xn2cn=a0bn+a1bn1+...=i=0naibni

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