• 多项式求逆 模板


    #include<cstdio>
    #include<cstring>
    #include<algorithm>
    using namespace std;
    #define N 300000
    #define md 998244353
    #define ll long long
    ll f[N], g[N], f0[N], g0[N];
    int rev[N];
    ll ksm(ll x, ll y) {
    	if(!y) return 1;
    	ll l = ksm(x, y / 2);
    	if(y % 2) return l * l % md * x % md;
    	return l * l % md;
    }
    void ntt(ll *a, int n, int r) {
    	for(int i = 0; i < n; i++) {
    		rev[i] = rev[i / 2] / 2 + (i & 1) * n / 2;
    		if(i < rev[i]) swap(a[i], a[rev[i]]);
    	}
    	for(int i = 2; i <= n; i *= 2) {
    		ll t = ksm(3, (md - 1) / i);
    		if(r == -1) t = ksm(t, md - 2);
    		for(int j = 0; j < n; j += i) {
    			ll s = 1;
    			for(int k = 0; k < i / 2; k++) {
    				ll A = a[j + k], B = a[j + i / 2 + k] * s % md;
    				a[j + k] = (A + B) % md;
    				a[j + i / 2 + k] = (A - B + md) % md;
    				s = s * t % md;
    			}
    		}
    	}
    	if(r == -1) {
    		ll v = ksm(n, md - 2);
    		for(int i = 0; i < n; i++) a[i] = (a[i] + md) * v % md;
    	}
    }
    int main() {
    	int n, i, j, k;
    	scanf("%d", &n);
    	for(i = 0; i < n; i++) scanf("%lld", &f[i]);
    	
    	int ns = 1;
    	while(ns <= n) ns *= 2;
    	
    	g[0] = ksm(f[0], md - 2);
    	for(i = 2; i <= ns; i *= 2) {
    		for(j = 0; j < i; j++) f0[j] = f[j], g0[j] = g[j], g0[j + i] = f0[j + i] = 0;
    		
    		ntt(f0, 2 * i, 1);
    		
    		ntt(g0, 2 * i, 1);
    		
    		for(j = 0; j < 2 * i; j++) g0[j] = g0[j] * g0[j] % md * f0[j] % md;
    		
    		ntt(g0, 2 * i, -1);
    		
    		for(j = 0; j < i; j++) g[j] = (g[j] * 2 - g0[j] + md) % md;
    	}
    	for(i = 0; i < n; i++) printf("%lld ", g[i]);
    	return 0;
    }
    
    哈哈哈哈哈哈哈哈哈哈
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  • 原文地址:https://www.cnblogs.com/LZA119/p/14623419.html
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