ZOJ3229 Shoot the Bullet

http://acm.hust.edu.cn/vjudge/problem/viewProblem.action?id=20756

思路：就讲一下有源汇上下界最大流的做法吧!对于所有的边，就按照无源汇的做法做，然后建一条(t->s，inf)的边，然后先算ss到tt的最大流，看是否满足下界，然后不管这个流的答案，清空cnt和dis，然后算出s->t的最大流，就是答案。

 #include<cstdio>
 #include<cmath>
 #include<iostream>
 #include<algorithm>
 #include<cstring>
 #define inf 0x7fffffff
 int dn[],id[];
 int tot,go[],next[],first[],flow[];
 int n,m,du[],op[],cnt[],dis[];
 int read(){
     int t=,f=;char ch=getchar();
     while (ch<''||ch>'') {if (ch=='-') f=-;ch=getchar();}
     while (''<=ch&&ch<=''){t=t*+ch-'';ch=getchar();}
     return t*f;
 }
 void insert(int x,int y,int z){
     tot++;
     go[tot]=y;
     next[tot]=first[x];
     first[x]=tot;
     flow[tot]=z;
 }
 void add(int x,int y,int z){
     insert(x,y,z);op[tot]=tot+;
     insert(y,x,);op[tot]=tot-;
 }
 int dfs(int x,int f,int S,int T,int nodes){
     int mn=nodes,sum=;
     if (x==T) return f;
     for (int i=first[x];i;i=next[i]){
       int pur=go[i];
       if (flow[i]&&dis[pur]+==dis[x]){
         int F=std::min(flow[i],f-sum);
         int save=dfs(pur,F,S,T,nodes);
         sum+=save;
         flow[i]-=save;
         flow[op[i]]+=save;
         if (sum==f||dis[S]>=nodes) return sum;
       }
       if (flow[i]) mn=std::min(mn,dis[pur]);
     }
     if (sum==){
       cnt[dis[x]]--;
     if (cnt[dis[x]]==){
       dis[S]=nodes;
     }else{
       dis[x]=mn+;
       cnt[dis[x]]++;
       }
     }
     return sum;
 }
 int mxflow(int S,int T,int nodes){
     int res=;
     for (int i=;i<=nodes;i++) cnt[i]=dis[i]=;
     while (dis[S]<nodes)
       res+=dfs(S,inf,S,T,nodes);
     return res;
 }
 int main(){
     freopen("tx.in","r",stdin);
     int Nodes=;
     while (~scanf("%d%d",&n,&m)){
       for (int i=;i<=Nodes;i++) first[i]=du[i]=;tot=;
       int s=n+m+,t=s+;
       int ss=t+,tt=ss+;
       for (int i=;i<=m;i++){
        int x=read();
        du[i]-=x;
        du[t]+=x;
        add(i,t,inf);
       }
      int Cnt=;
      for (int i=;i<=n;i++){
      int c=read(),d=read();
      add(s,i+m,d);
      while (c--){
        int x=read(),l=read(),r=read();
        du[i+m]-=l;
        du[x+]+=l;
        dn[++Cnt]=l;id[Cnt]=tot+;
        add(i+m,x+,r-l);
      }
      }
      int sum=;
      for (int i=;i<=t;i++)
      if (du[i]>) add(ss,i,du[i]),sum+=du[i];
      else add(i,tt,-du[i]);
      add(t,s,inf);
      if (sum!=mxflow(ss,tt,tt)) puts("-1");
      else{
       printf("%d\n",mxflow(s,t,tt));
      for (int i=;i<=Cnt;i++)
       printf("%d\n",dn[i]+flow[op[id[i]]]);
      }
      puts("");
      Nodes=tt;
     }
 }

**，没看到可能有多解，害我调了好久。。