3931: [CQOI2015]网络吞吐量【网络流】

  1 #include<iostream>
  2 #include<cstdio>
  3 #include<cstring>
  4 #include<queue>
  5 #define maxn 400009
  6 #define inf ((1LL<<63)-1)
  7 #define ll long long
  8 using namespace std;
  9 ll head[maxn],next[maxn],point[maxn],now,p[maxn],flow[maxn];
 10 ll n,m,value[maxn],dist[maxn],dis[maxn],x[maxn],y[maxn],v[maxn];
 11 void add(ll x,ll y,ll v)
 12 {
 13     next[++now]=head[x];
 14     head[x]=now;
 15     point[now]=y;
 16     value[now]=v;
 17 }
 18 void add2(ll x,ll y,ll v)
 19 {
 20     next[++now]=head[x];
 21     head[x]=now;
 22     point[now]=y;
 23     flow[now]=v;
 24     next[++now]=head[y];
 25     head[y]=now;
 26     point[now]=x;
 27     flow[now]=0;
 28 }
 29 void spfa(ll s)
 30 {
 31     memset(dist,-1,sizeof(dist));
 32     int visit[maxn]={0};
 33     visit[s]=1;
 34     queue<ll>q;
 35     q.push(s);
 36     dist[s]=0;
 37     while(!q.empty())
 38     {
 39         int u=q.front();
 40         q.pop();
 41         visit[u]=0;
 42         for(int i=head[u];i;i=next[i])
 43         {
 44             ll k=point[i];
 45             if(dist[k]==-1 || dist[u]+value[i]<dist[k])
 46             {
 47                 dist[k]=dist[u]+value[i];
 48                 p[k]=u;
 49                 if(!visit[k])
 50                 {
 51                     visit[k]=1;
 52                     q.push(k);
 53                 }
 54             }
 55         }
 56     }
 57 }
 58 int bfs(ll s,ll t)
 59 {
 60     queue<ll>q;
 61     memset(dis,-1,sizeof(dis));
 62     q.push(s);
 63     dis[s]=0;
 64     while(!q.empty())
 65     {
 66         ll u=q.front();
 67         q.pop();
 68         for(int i=head[u];i;i=next[i])
 69         {
 70             ll k=point[i];
 71             if(dis[k]==-1 && flow[i])
 72             {
 73                 dis[k]=dis[u]+1;
 74                 q.push(k);
 75             }
 76         }
 77     }
 78     return dis[t]!=-1;
 79 }
 80 ll dfs(ll s,ll d,ll t)
 81 {
 82     if(s==t)return d;
 83     ll res=0;
 84     for(int i=head[s];i&&res<d;i=next[i])
 85     {
 86         ll u=point[i];
 87         if(flow[i] && dis[u]==dis[s]+1)
 88         {
 89             ll dd=dfs(u,min(flow[i],d-res),t);
 90             if(dd)
 91             {
 92                 flow[i]-=dd;
 93                 flow[((i-1)^1)+1]+=dd;
 94                 res+=dd;
 95             }
 96         }
 97     }
 98     if(res==0)dis[s]=-1;
 99     return res;
100 }
101 int main()
102 {
103         scanf("%lld%lld",&n,&m);
104         for(int i=1;i<=m;i++)
105         {
106                 scanf("%lld%lld%lld",&x[i],&y[i],&v[i]);
107                 add(x[i],y[i],v[i]);
108                 add(y[i],x[i],v[i]);
109         }
110         spfa(1);
111         memset(head,0,sizeof(head));now=0;
112     for(int i=1;i<=m;i++)
113     {
114         if(dist[x[i]] + v[i] == dist[y[i]])
115         {
116             add2(x[i]+n,y[i],inf);
117         }
118         if(dist[y[i]] + v[i] == dist[x[i]])
119         {
120             add2(y[i]+n,x[i],inf);
121         }
122     }
123     ll b;
124         for(int i=1;i<=n;i++)
125     {
126         scanf("%lld",&b);
127         add2(i,i + n,(i==1||i==n)?inf:b);
128     }
129     ll ans=0;
130     while(bfs(1 ,n + n))
131     {
132         ans += dfs(1 ,inf ,n + n);
133     }
134     printf("%lld\n",ans);
135         return 0;
136 }