[poj 3281]最大流+建图很巧妙

题目链接：http://poj.org/problem?id=3281

看了kuangbin大佬的思路，还用着kuangbin板子orz   http://www.cnblogs.com/kuangbin/archive/2012/08/21/2649850.html

#include<cstdio>
#include<cstring>
using namespace std;

const int MAXN = 10010;
const int MAXM = 40010;
const int INF = 0x3f3f3f3f;
struct Edge
{
    int to,next,cap,flow;
} edge[MAXM];
int tol;
int head[MAXN];
int gap[MAXN],dep[MAXN],pre[MAXN],cur[MAXN];
void init()
{
    tol = 0;
    memset(head,-1,sizeof(head));
}
void addedge(int u,int v,int w,int rw=0)
{
    edge[tol].to = v;
    edge[tol].cap = w;
    edge[tol].next = head[u];
    edge[tol].flow = 0;
    head[u] = tol++;
    edge[tol].to = u;
    edge[tol].cap = rw;
    edge[tol].next = head[v];
    edge[tol].flow = 0;
    head[v]=tol++;
}
int sap(int start,int end,int N)
{
    memset(gap,0,sizeof(gap));
    memset(dep,0,sizeof(dep));
    memcpy(cur,head,sizeof(head));
    int u = start;
    pre[u] = -1;
    gap[0] = N;
    int ans = 0;
    while(dep[start] < N)
    {
        if(u == end)
        {
            int Min = INF;
            for(int i = pre[u]; i != -1; i = pre[edge[i^1].to])
                if(Min > edge[i].cap - edge[i].flow)
                    Min = edge[i].cap - edge[i].flow;
            for(int i = pre[u]; i != -1; i = pre[edge[i^1].to])
            {
                edge[i].flow += Min;
                edge[i^1].flow -= Min;
            }
            u = start;
            ans += Min;
            continue;
        }
        bool flag = false;
        int v;
        for(int i = cur[u]; i != -1; i = edge[i].next)
        {
            v = edge[i].to;
            if(edge[i].cap - edge[i].flow && dep[v]+1 == dep[u])
            {
                flag = true;
                cur[u] = pre[v] = i;
                break;
            }
        }
        if(flag)
        {
            u = v;
            continue;
        }
        int Min = N;
        for(int i = head[u]; i != -1; i = edge[i].next)
            if(edge[i].cap - edge[i].flow && dep[edge[i].to] < Min)
            {
                Min = dep[edge[i].to];
                cur[u] = i;
            }
        gap[dep[u]]--;
        if(!gap[dep[u]])return ans;
        dep[u] = Min+1;
        gap[dep[u]]++;
        if(u != start) u = edge[pre[u]^1].to;
    }
    return ans;
}

int main()
{
    int n,F,D;
    scanf("%d%d%d",&n,&F,&D);
    init();
    for (int i=0;i<n;i++) addedge(i,i+n,1);
    for (int i=0;i<n;i++)
    {
        int f,d;
        scanf("%d%d",&f,&d);
        for (int j=0;j<f;j++)
        {
            int x;
            scanf("%d",&x);
            x--;
            addedge(n+n+x,i,1);
        }
        for (int j=0;j<d;j++)
        {
            int x;
            scanf("%d",&x);
            x--;
            addedge(n+i,n+n+F+x,1);
        }
    }
    for (int i=0;i<F;i++) addedge(n+n+F+D,n+n+i,1);
    for (int i=0;i<D;i++) addedge(n+n+F+i,n+n+F+D+1,1);
    printf("%d",sap(n+n+F+D,n+n+F+D+1,n+n+F+D+2));
    return 0;
}