【USACO】Dining

【题目链接】

【JZXX】点击打开链接

【caioj】点击打开链接

【算法】

拆点+网络流

【代码】

#include<bits/stdc++.h>
using namespace std;
#define MAXN 1000

int i,tot,N,F,D,sf,sd,ans,x;
int U[MAXN*],V[MAXN*],W[MAXN*],Head[MAXN*],
        Next[MAXN*],other[MAXN*],h[MAXN*];

template <typename T> void read(T &x) {
        int f=; x = ;
        char c = getchar();
        for (; !isdigit(c); c = getchar()) { if (c=='-') f=-; }
        for (; isdigit(c); c = getchar()) x=x*+c-'';
        x*=f;
}

inline void add(int a,int b,int c) {
        ++tot;
        U[tot] = a; V[tot] = b; W[tot] = c;
        Next[tot] = Head[a]; Head[a] = tot;
        other[tot] = tot + ;
        ++tot;
        U[tot] = b; V[tot] = a; W[tot] = ;
        Next[tot] = Head[b]; Head[b] = tot;
        other[tot] = tot - ;
}

inline bool BFS() {
        int i,x,y;
        queue<int> q;
        memset(h,,sizeof(h));
        h[] = ; q.push();
        while (!q.empty()) {
                x = q.front(); q.pop();
                for (i = Head[x]; i; i = Next[i]) {
                        y = V[i];
                        if ((W[i] > ) && (!h[y])) {
                                h[y] = h[x] + ;
                                q.push(y);
                        }
                }
        }
        if (h[F+*N+D+]) return true;
        else return false;
}

int maxflow(int x,int f) {
        int i,y,s=,t;
        if (x == F +  * N + D + ) return f;
        for (i = Head[x]; i; i = Next[i]) {
                y = V[i];
                if ((W[i] > ) && (h[y] == h[x] + ) && (s < f)) {
                        s += (t = maxflow(y,min(W[i],f-s)));
                        W[i] -= t; W[other[i]] += t;
                }
        }
        if (!s) h[x] = ;
        return s;
}

int main() {

        read(N); read(F); read(D);
        for (i = ; i <= F; i++) add(,+i,);
        for (i = ; i <= D; i++) add(+F+*N+i,F+*N+D+,);
        for (i = ; i <= N; i++) add(+F+i,+F+N+i,);
        for (i = ; i <= N; i++) {
                read(sf); read(sd);
                while (sf--) {
                        read(x);
                        add(+x,i+F+,);
                }
                while (sd--) {
                        read(x);
                        add(+F+N+i,+F+*N+x,);
                }
        }

        while (BFS()) {
                ans += maxflow(,2e9);
        }

        cout<< ans << endl;

        return ;

}