• [SDOI2013]方程


    (geq x)的条件直接减掉。
    (leq x)的容斥。
    (exlucas)

    #include<iostream>
    #include<cstdio>
    #define ll long long 
    
    void exgcd(ll a,ll b,ll &x,ll &y){
        if (!b) return (void)(x=1,y=0);
        exgcd(b,a%b,x,y);
        ll tmp=x;x=y;y=tmp-a/b*y;
    }
    
    ll gcd(ll a,ll b){
    	if(b == 0)return a;
    	return gcd(b,a % b);
    }
    
    inline ll inv(ll a,ll p){
    	ll x,y;
    	exgcd(a,p,x,y);
    	return (x + p) % p;
    }
    
    inline ll lcm(ll a,ll b){
    	return a / gcd(a,b) * b;
    }
    
    inline ll fastpow(ll a,ll b,ll p){
    	ll ans = 1;
    	a %= p;
    	while(b){
    		if(b & 1)ans = (ans * a) % p;
    		b >>= 1;
    		a = (a * a) % p;
    	}
    	return ans;
    }
    
    inline ll read(){
    	ll ans = 0;
    	char a = getchar();
    	while(!(a <= '9' && a >= '0'))a = getchar();
    	while(a <= '9' && a >= '0')ans = (ans << 3) + (ans << 1) + (a - '0'),a = getchar();
    	return ans;
    }
    
    inline ll f(ll n,ll p,ll pk){
    	if(n == 0)return 1;
    	ll rou = 1;
    	ll res = 1;
    	for(ll i = 1;i <= pk;++i)
    	if(i % p)rou = rou * i % pk;
    	rou = fastpow(rou,n / pk,pk);
    	for(ll i = pk * (n / pk);i <= n;++i)
    	if(i % p)res = res * (i % pk) % pk;
    	return f(n / p,p,pk) * rou % pk * res % pk;
    }
    
    inline ll g(ll n,ll p){
    	if(n < p)return 0;
    	return g(n / p,p) + (n / p);
    }
    
    inline ll c_pk(ll n,ll m,ll p,ll pk){
    	ll fn = f(n,p,pk),fm = inv(f(m,p,pk),pk),fnm = inv(f(n - m,p,pk),pk);
    	ll mi = fastpow(p,g(n,p) - g(m,p) - g(n - m,p),pk);
    	return fn % pk * fm % pk * fnm % pk * mi % pk;
    }
    
    ll A[1001],B[1001];
    
    // x = B(mod A)
    
    inline ll exlucas(ll n,ll m,ll p){
    	if(n < m || n <= 0)return 0;
    	ll P = p,tot = 0;
    	for(ll i = 2;i * i <= P;++i){
    		if(!(p % i)){
    			ll pk = 1;
    			while(!(p % i))
    			pk *= i,p /= i;
    			A[++tot] = pk;
    			B[tot] = c_pk(n,m,i,pk);
    		}
    	}
    	if(p != 1)
    	A[++tot] = p,B[tot] = c_pk(n,m,p,p);
    	ll ans = 0;
    	for(ll i = 1;i <= tot;++i){
    		ll M = P / A[i],t = inv(M,A[i]);
    		ans = (ans + B[i] * M % P * t % P) % P;
    	}
    	return ans;
    }
    
    ll a[200];
    
    int main(){
    	ll T,p;
    	scanf("%lld%lld",&T,&p);
    	while(T -- ){
    		ll n,n1,n2,m,ans = 0;
    		scanf("%lld%lld%lld%lld",&n,&n1,&n2,&m);
    		for(int i = 1;i <= n1;++i)
    		scanf("%lld",&a[i]);
    		for(int i = 1;i <= n2;++i){
    			ll x;
    			scanf("%lld",&x);
    			m -= x - 1; 
    		}
    		for(int S = 0;S < (1ll << n1);++S){
    			int cnt = 0;
    			ll tmp = m;
    			for(int i = 0;i <= n1 - 1;++i)
    			if((S >> i) & 1)++cnt,tmp -= a[i + 1];
    			ans = (ans + (cnt & 1 ? -1 : 1) * exlucas(tmp - 1,n - 1,p) % p) % p;
    		}
    		std::cout<<(ans + p) % p<<std::endl;
    	}
    }
    
    
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  • 原文地址:https://www.cnblogs.com/dixiao/p/15244899.html
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