sgu 176 有源汇有上下界的最小流模板题

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/*参考博文:http://hi.baidu.com/dragon_eric123/item/82e259200ece744046996282  有上下界的有源最小流*/#include<stdio.h>#include<string.h>#include<queue>using namespace  std;#define N 300#define inf 0x3fffffffstruct node {int u,v,w,f,next;}bian[N*N*2];int head[N],yong,dis[N],work[N];void init(){yong=0;memset(head,-1,sizeof(head));}void addbian(int u,int v,int w,int f) {bian[yong].u=u;bian[yong].v=v;bian[yong].w=w;bian[yong].f=f;bian[yong].next=head[u];head[u]=yong++;}void add(int u,int v,int w,int f) {addbian(u,v,w,f);addbian(v,u,0,f);}int min(int a,int b){    return a<b?a:b;}int bfs(int s,int t){    memset(dis,-1,sizeof(dis));    queue<int>q;    q.push(s);    dis[s]=0;    while(!q.empty())    {        int u=q.front();        q.pop();        for(int i=head[u];i!=-1;i=bian[i].next)        {            int v=bian[i].v;            if(bian[i].w&&dis[v]==-1)            {                dis[v]=dis[u]+1;                q.push(v);                if(v==t)                    return 1;            }        }    }    return 0;}int dfs(int  s,int limit,int t){    if(s==t)return limit;    for(int &i=work[s];i!=-1;i=bian[i].next)    {        int v=bian[i].v;        if(bian[i].w&&dis[v]==dis[s]+1)        {            int tt=dfs(v,min(limit,bian[i].w),t);            if(tt)            {                bian[i].w-=tt;                bian[i^1].w+=tt;                return tt;            }        }    }    return 0;}int dinic(int s,int t){    int ans=0;    while(bfs(s,t))    {        memcpy(work,head,sizeof(head));        while(int tt=dfs(s,inf,t))            ans+=tt;    }    return ans;}int main() {   int n,m,i,a,b,c,d,w[N],sum,f,ff,index,s,t;   while(scanf("%d%d",&n,&m)!=EOF) {    init();    s=0;t=n+1;sum=0;    memset(w,0,sizeof(w));   for(i=0;i<m;i++) {        scanf("%d%d%d%d",&a,&b,&c,&d);          if(d){          add(a,b,0,c);          w[a]-=c;          w[b]+=c;          }          else            add(a,b,c,c);    }    for(i=1;i<=n;i++) {        if(w[i]>0) {            sum+=w[i];            add(s,i,w[i],0);        }        else add(i,t,-w[i],0);    }    f=dinic(s,t);    index=yong;    add(n,1,inf,0);    ff=dinic(s,t);    if(f+ff!=sum)        printf("Impossible\n");    else {        printf("%d\n",bian[index^1].w);        for(i=0;i<m-1;i++)            printf("%d ",bian[i*2].f-bian[i*2].w);        printf("%d\n",bian[i*2].f-bian[i*2].w);    }   }return 0;}
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