POJ 2125 Destroying The Graph

传送门：POJ 2125

#include <cstdio>#include <cstring>#include <cstdlib>#include <iostream>#define N 300#define M 20000#define INF 99999999using namespace std;int to[M],next[M],head[N],len[M],cnt,layer[N],n,m,S,T,q[M];bool vis[N];inline void add(int u,int v,int w){    to[cnt]=v; len[cnt]=w; next[cnt]=head[u]; head[u]=cnt++;    to[cnt]=u; len[cnt]=0; next[cnt]=head[v]; head[v]=cnt++;}void read(){    memset(head,-1,sizeof head);cnt=0;    scanf("%d%d",&n,&m);    S=0,T=n+n+1;    for(int i=1,a;i<=n;i++) scanf("%d",&a),add(i+n,T,a);    for(int i=1,a;i<=n;i++) scanf("%d",&a),add(S,i,a);    for(int i=1,a,b;i<=m;i++) scanf("%d%d",&a,&b),add(a,b+n,INF);}bool bfs(){    memset(layer,-1,sizeof layer);    int h=1,t=2,sta;    q[1]=S; layer[S]=0;    while(h<t)    {        sta=q[h++];        for(int i=head[sta];~i;i=next[i])            if(len[i]>0&&layer[to[i]]<0)            {                layer[to[i]]=layer[sta]+1;                q[t++]=to[i];            }    }    return layer[T]!=-1;}int Find(int u,int cur_flow){    if(u==T) return cur_flow;    int result=0,tmp;    for(int i=head[u];~i;i=next[i])        if(len[i]>0&&layer[to[i]]==layer[u]+1)        {            tmp=Find(to[i],min(cur_flow-result,len[i]));            len[i]-=tmp; len[i^1]+=tmp; result+=tmp;        }    if(!result) layer[u]=-1;    return result;}void dfs(int u){    vis[u]=true;    for(int i=head[u];~i;i=next[i])        if(!vis[to[i]]&&len[i])            dfs(to[i]);}void dinic(){    int ans=0;    while(bfs()) ans+=Find(S,INF);    printf("%d\n",ans);    dfs(S);    ans=0;    for(int i=1;i<=n;i++)        ans+=(!vis[i])+(vis[i+n]);       printf("%d\n",ans);    for(int i=1;i<=n;i++)    {        if(!vis[i]) printf("%d -\n",i);        if(vis[i+n]) printf("%d +\n",i);    }}int main(){    read();    dinic();    return 0;}