• 洛谷P4233 射命丸文的笔记 【多项式求逆】


    题目链接

    洛谷P4233

    题解

    我们只需求出总的哈密顿回路个数和总的强联通竞赛图个数

    对于每条哈密顿回路,我们统计其贡献
    一条哈密顿回路就是一个圆排列,有(frac{n!}{n})种,剩余边随便连
    所以总的贡献为

    [(n - 1)!2^{{n choose 2} - n} ]

    我们只需求出总的强联通竞赛图的个数
    (g[n])表示(n)个点竞赛图个数,(f[n])表示强联通竞赛图个数
    那么有

    [g[n] = sumlimits_{i = 1}^{n}{n choose i}f[i]g[n - i] ]

    [frac{g[n]}{n!} = sumlimits_{i = 1}^{n}frac{f[i]}{i!}frac{g[n - i]}{(n - i)!} ]

    (G(x))(F(x))分别为其指数型生成函数
    那么有

    [G(x) = F(x)G(x) + 1 ]

    [F(x) = frac{G(x) - 1}{G(x)} ]

    多项式求逆即可
    复杂度(O(nlogn))

    #include<algorithm>
    #include<iostream>
    #include<cstdlib>
    #include<cstring>
    #include<cstdio>
    #include<vector>
    #include<queue>
    #include<cmath>
    #include<map>
    #define LL long long int
    #define REP(i,n) for (int i = 1; i <= (n); i++)
    #define Redge(u) for (int k = h[u],to; k; k = ed[k].nxt)
    #define cls(s,v) memset(s,v,sizeof(s))
    #define mp(a,b) make_pair<int,int>(a,b)
    #define cp pair<int,int>
    using namespace std;
    const int maxn = 400005,maxm = 100005,INF = 0x3f3f3f3f;
    inline int read(){
    	int out = 0,flag = 1; char c = getchar();
    	while (c < 48 || c > 57){if (c == '-') flag = 0; c = getchar();}
    	while (c >= 48 && c <= 57){out = (out << 1) + (out << 3) + c - 48; c = getchar();}
    	return flag ? out : -out;
    }
    const int P = 998244353,G = 3;
    inline int qpow(int a,LL b){
    	int re = 1;
    	for (; b; b >>= 1,a = 1ll * a * a % P)
    		if (b & 1) re = 1ll * re * a % P;
    	return re;
    }
    inline LL C(int n){return 1ll * n * (n - 1) / 2;}
    int R[maxn];
    void NTT(int* a,int n,int f){
    	for (int i = 0; i < n; i++) if (i < R[i]) swap(a[i],a[R[i]]);
    	for (int i = 1; i < n; i <<= 1){
    		int gn = qpow(G,(P - 1) / (i << 1));
    		for (int j = 0; j < n; j += (i << 1)){
    			int g = 1,x,y;
    			for (int k = 0; k < i; k++,g = 1ll * g * gn % P){
    				x = a[j + k],y = 1ll * g * a[j + k + i] % P;
    				a[j + k] = (x + y) % P,a[j + k + i] = ((x - y) % P + P) % P;
    			}
    		}
    	}
    	if (f == 1) return;
    	int nv = qpow(n,P - 2); reverse(a + 1,a + n);
    	for (int i = 0; i < n; i++) a[i] = 1ll * a[i] * nv % P;
    }
    int A[maxn],B[maxn],c[maxn],ans,N,fac[maxn],inv[maxn],fv[maxn];
    void init(){
    	fac[0] = fac[1] = inv[0] = inv[1] = fv[0] = fv[1] = 1;
    	for (int i = 2; i <= N; i++){
    		fac[i] = 1ll * fac[i - 1] * i % P;
    		inv[i] = 1ll * (P - P / i) * inv[P % i] % P;
    		fv[i] = 1ll * fv[i - 1] * inv[i] % P;
    	}
    }
    void Inv(int deg,int* a,int* b){
        if (deg == 1){b[0] = qpow(a[0],P - 2); return;}
        Inv((deg + 1) >> 1,a,b);
        int L = 0,n = 1;
        while (n < (deg << 1)) n <<= 1,L++;
        for (int i = 1; i < n; i++) R[i] = (R[i >> 1] >> 1) | ((i & 1) << (L - 1));
        for (int i = 0; i < deg; i++) c[i] = a[i];
        for (int i = deg; i < n; i++) c[i] = 0;
        NTT(c,n,1); NTT(b,n,1);
        for (int i = 0; i < n; i++)
            b[i] = 1ll * ((2ll - 1ll * c[i] * b[i] % P) + P) % P * b[i] % P;
        NTT(b,n,-1);
        for (int i = deg; i < n; i++) b[i] = 0;
    }
    int main(){
    	N = read(); init();
    	for (int i = 0; i <= N; i++) A[i] = 1ll * qpow(2,C(i)) * fv[i] % P;
    	Inv(N + 1,A,B);
    	A[0] = 0;
    	int n = 1,L = 0;
    	while (n <= (N << 1)) n <<= 1,L++;
    	for (int i = 1; i < n; i++) R[i] = (R[i >> 1] >> 1) | ((i & 1) << (L - 1));
    	NTT(A,n,1); NTT(B,n,1);
    	for (int i = 0; i < n; i++) A[i] = 1ll * A[i] * B[i] % P;
    	NTT(A,n,-1);
    	REP(i,N){
    		if (i == 1) puts("1");
    		else if (i == 2) puts("-1");
    		else printf("%lld
    ",1ll * fac[i - 1] * qpow(2,C(i) - i) % P * qpow(1ll * A[i] * fac[i] % P,P - 2) % P);
    	}
    	return 0;
    }
    
    
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  • 原文地址:https://www.cnblogs.com/Mychael/p/9282436.html
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